Convert.ToBoolean 方法

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::SByte value);

[System.CLSCompliant(false)]
public static bool ToBoolean (sbyte value);

[<System.CLSCompliant(false)>]
static member ToBoolean : sbyte -> bool

Public Shared Function ToBoolean (value As SByte) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

屬性

CLSCompliantAttribute

範例

下列範例會將值的陣列 SByte 轉換成 Boolean 值。

array<SByte>^ numbers = gcnew array<SByte> { SByte::MinValue, -1, 0, 10, 100, SByte::MaxValue };
bool result;
   
for each (SByte number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-5}  -->  {1}", number, result);
}
// The example displays the following output:
//       -128   -->  True
//       -1     -->  True
//       0      -->  False
//       10     -->  True
//       100    -->  True
//       127    -->  True

sbyte[] numbers = { SByte.MinValue, -1, 0, 10, 100, SByte.MaxValue };
bool result;

foreach (sbyte number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-5}  -->  {1}", number, result);
}
// The example displays the following output:
//       -128   -->  True
//       -1     -->  True
//       0      -->  False
//       10     -->  True
//       100    -->  True
//       127    -->  True

let numbers = 
    [| SByte.MinValue; -1y; 0y
       10y; 100y; SByte.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-5}  -->  {result}"
// The example displays the following output:
//       -128   -->  True
//       -1     -->  True
//       0      -->  False
//       10     -->  True
//       100    -->  True
//       127    -->  True

Dim numbers() As SByte = { SByte.MinValue, -1, 0, 10, 100, SByte.MaxValue }
Dim result As Boolean

For Each number As SByte In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-5}  -->  {1}", number, result)
Next
' The example displays the following output:
'       -128   -->  True
'       -1     -->  True
'       0      -->  False
'       10     -->  True
'       100    -->  True
'       127    -->  True

另請參閱

• SByte

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::String ^ value, IFormatProvider ^ provider);

public static bool ToBoolean (string value, IFormatProvider provider);

public static bool ToBoolean (string? value, IFormatProvider? provider);

static member ToBoolean : string * IFormatProvider -> bool

Public Shared Function ToBoolean (value As String, provider As IFormatProvider) As Boolean

參數

傳回

當 true 等於 value 時為 TrueString，否則，當 false 等於 value 或 FalseString 時，則為 null。

例外狀況

備註

如果您不想在轉換失敗時處理例外狀況，您可以改為呼叫 Boolean.TryParse 方法。 它會傳回值 Boolean ，指出轉換成功或失敗。

另請參閱

• String

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::Object ^ value, IFormatProvider ^ provider);

public static bool ToBoolean (object value, IFormatProvider provider);

public static bool ToBoolean (object? value, IFormatProvider? provider);

static member ToBoolean : obj * IFormatProvider -> bool

Public Shared Function ToBoolean (value As Object, provider As IFormatProvider) As Boolean

參數

傳回

true 或 false，其會反映為 ToBoolean(IFormatProvider) 的基礎類型所叫用之 value 方法所傳回的值。 如果 value 是 null，則方法會傳回 false。

例外狀況

範例

下列範例會定義實作 IConvertible 的類別，以及實作 的 IFormatProvider類別。 實 IConvertible 作的類別物件會保存值的陣列 Double 。 每個類別的物件都會傳遞至 ToBoolean(Object, IFormatProvider) 方法。 如果任何未捨棄的陣列值為非零，這個方法會 true 傳回 。 對象 IFormatProvider 會決定針對這個計算捨棄元素的方式。

using namespace System;
using namespace System::Collections;

// Define the types of averaging available in the class 
// implementing IConvertible.
public enum class AverageType : short
{
   None = 0,
   GeometricMean = 1,
   ArithmeticMean = 2,
   Median = 3
};


// Pass an instance of this class to methods that require an 
// IFormatProvider. The class instance determines the type of 
// average to calculate.
ref class AverageInfo: public IFormatProvider
{
protected:
   AverageType AvgType;

public:

   // Specify the type of averaging in the constructor.
   AverageInfo( AverageType avgType )
   {
      this->AvgType = avgType;
   }


   // This method returns a reference to the containing object 
   // if an object of AverageInfo type is requested. 
   virtual Object^ GetFormat( Type^ argType )
   {
      if ( argType == AverageInfo::typeid)
            return this;
      else
            return (Object^)0;
   }


   property AverageType TypeOfAverage 
   {

      // Use this property to set or get the type of averaging.
      AverageType get()
      {
         return this->AvgType;
      }

      void set( AverageType value )
      {
         this->AvgType = value;
      }

   }

};


// This class encapsulates an array of double values and implements 
// the IConvertible interface. Most of the IConvertible methods 
// return an average of the array elements in one of three types: 
// arithmetic mean, geometric mean, or median. 
ref class DataSet: public IConvertible
{
private:
   static Object^ null = nullptr;

protected:
   ArrayList^ data;
   AverageInfo^ defaultProvider;

   // This method unboxes a boxed double.
   double UnBoxDouble( Object^ obj )
   {
      return  *static_cast<double^>(obj);
   }


public:

   // Construct the object and add an initial list of values.
   // Create a default format provider.
   DataSet( ... array<Double>^values )
   {
      data = gcnew ArrayList( (Array^)values );
      defaultProvider = gcnew AverageInfo( AverageType::ArithmeticMean );
   }


   // Add additional values with this method.
   int Add( double value )
   {
      data->Add( value );
      return data->Count;
   }


   property double Item[ int ]
   {

      // Get, set, and add values with this indexer property.
      double get( int index )
      {
         if ( index >= 0 && index < data->Count )
                  return UnBoxDouble( data[ index ] );
         else
                  throw gcnew InvalidOperationException( "[DataSet.get] Index out of range." );
      }

      void set( int index, double value )
      {
         if ( index >= 0 && index < data->Count )
                  data[ index ] = value;
         else
         if ( index == data->Count )
                  data->Add( value );
         else
                  throw gcnew InvalidOperationException( "[DataSet.set] Index out of range." );
      }

   }

   property int Count 
   {

      // This property returns the number of elements in the object.
      int get()
      {
         return data->Count;
      }

   }

protected:

   // This method calculates the average of the object's elements.
   double Average( AverageType avgType )
   {
      double SumProd;
      if ( data->Count == 0 )
            return 0.0;

      switch ( avgType )
      {
         case AverageType::GeometricMean:
            SumProd = 1.0;
            for ( int Index = 0; Index < data->Count; Index++ )
               SumProd *= UnBoxDouble( data[ Index ] );
            
            // This calculation will not fail with negative 
            // elements.
            return Math::Sign( SumProd ) * Math::Pow( Math::Abs( SumProd ), 1.0 / data->Count );

         case AverageType::ArithmeticMean:
            SumProd = 0.0;
            for ( int Index = 0; Index < data->Count; Index++ )
               SumProd += UnBoxDouble( data[ Index ] );
            return SumProd / data->Count;

         case AverageType::Median:
            if ( data->Count % 2 == 0 )
                        return (UnBoxDouble( data[ data->Count / 2 ] ) + UnBoxDouble( data[ data->Count / 2 - 1 ] )) / 2.0;
            else
                        return UnBoxDouble( data[ data->Count / 2 ] );

         default:
            return 0.0;
      }
   }


   // Get the AverageInfo object from the caller's format provider,
   // or use the local default.
   AverageInfo^ GetAverageInfo( IFormatProvider^ provider )
   {
      AverageInfo^ avgInfo = nullptr;
      if ( provider != nullptr )
            avgInfo = static_cast<AverageInfo^>(provider->GetFormat( AverageInfo::typeid ));

      if ( avgInfo == nullptr )
            return defaultProvider;
      else
            return avgInfo;
   }


   // Calculate the average and limit the range.
   double CalcNLimitAverage( double min, double max, IFormatProvider^ provider )
   {
      
      // Get the format provider and calculate the average.
      AverageInfo^ avgInfo = GetAverageInfo( provider );
      double avg = Average( avgInfo->TypeOfAverage );
      
      // Limit the range, based on the minimum and maximum values 
      // for the type.
      return avg > max ? max : avg < min ? min : avg;
   }


public:

   // The following elements are required by IConvertible.
   // None of these conversion functions throw exceptions. When
   // the data is out of range for the type, the appropriate
   // MinValue or MaxValue is used.
   virtual TypeCode GetTypeCode()
   {
      return TypeCode::Object;
   }

   virtual bool ToBoolean( IFormatProvider^ provider )
   {
      
      // ToBoolean is false if the dataset is empty.
      if ( data->Count <= 0 )
            return false;
      // For median averaging, ToBoolean is true if any 
      // non-discarded elements are nonzero.
      else
      
      // For median averaging, ToBoolean is true if any 
      // non-discarded elements are nonzero.
      if ( AverageType::Median == GetAverageInfo( provider )->TypeOfAverage )
      {
         if ( data->Count % 2 == 0 )
                  return (UnBoxDouble( data[ data->Count / 2 ] ) != 0.0 || UnBoxDouble( data[ data->Count / 2 - 1 ] ) != 0.0);
         else
                  return UnBoxDouble( data[ data->Count / 2 ] ) != 0.0;
      }
      // For arithmetic or geometric mean averaging, ToBoolean is 
      // true if any element of the dataset is nonzero.  
      else
      {
         for ( int Index = 0; Index < data->Count; Index++ )
            if ( UnBoxDouble( data[ Index ] ) != 0.0 )
                        return true;
         return false;
      }
   }

   virtual Byte ToByte( IFormatProvider^ provider )
   {
      return Convert::ToByte( CalcNLimitAverage( Byte::MinValue, Byte::MaxValue, provider ) );
   }

   virtual Char ToChar( IFormatProvider^ provider )
   {
      return Convert::ToChar( Convert::ToUInt16( CalcNLimitAverage( Char::MinValue, Char::MaxValue, provider ) ) );
   }


   // Convert to DateTime by adding the calculated average as 
   // seconds to the current date and time. A valid DateTime is 
   // always returned.
   virtual DateTime ToDateTime( IFormatProvider^ provider )
   {
      double seconds = Average( GetAverageInfo( provider )->TypeOfAverage );
      try
      {
         return DateTime::Now.AddSeconds( seconds );
      }
      catch ( ArgumentOutOfRangeException^ ) 
      {
         return seconds < 0.0 ? DateTime::MinValue : DateTime::MaxValue;
      }

   }

   virtual Decimal ToDecimal( IFormatProvider^ provider )
   {
      
      // The Double conversion rounds Decimal.MinValue and 
      // Decimal.MaxValue to invalid Decimal values, so the 
      // following limits must be used.
      return Convert::ToDecimal( CalcNLimitAverage(  -79228162514264330000000000000.0, 79228162514264330000000000000.0, provider ) );
   }

   virtual double ToDouble( IFormatProvider^ provider )
   {
      return Average( GetAverageInfo( provider )->TypeOfAverage );
   }

   virtual short ToInt16( IFormatProvider^ provider )
   {
      return Convert::ToInt16( CalcNLimitAverage( Int16::MinValue, Int16::MaxValue, provider ) );
   }

   virtual int ToInt32( IFormatProvider^ provider )
   {
      return Convert::ToInt32( CalcNLimitAverage( Int32::MinValue, Int32::MaxValue, provider ) );
   }

   virtual __int64 ToInt64( IFormatProvider^ provider )
   {
      
      // The Double conversion rounds Int64.MinValue and 
      // Int64.MaxValue to invalid Int64 values, so the following 
      // limits must be used.
      return Convert::ToInt64( CalcNLimitAverage(  -9223372036854775000, 9223372036854775000, provider ) );
   }

   virtual signed char ToSByte( IFormatProvider^ provider )
   {
      return Convert::ToSByte( CalcNLimitAverage( SByte::MinValue, SByte::MaxValue, provider ) );
   }

   virtual float ToSingle( IFormatProvider^ provider )
   {
      return Convert::ToSingle( CalcNLimitAverage( Single::MinValue, Single::MaxValue, provider ) );
   }

   virtual UInt16 ToUInt16( IFormatProvider^ provider )
   {
      return Convert::ToUInt16( CalcNLimitAverage( UInt16::MinValue, UInt16::MaxValue, provider ) );
   }

   virtual UInt32 ToUInt32( IFormatProvider^ provider )
   {
      return Convert::ToUInt32( CalcNLimitAverage( UInt32::MinValue, UInt32::MaxValue, provider ) );
   }

   virtual UInt64 ToUInt64( IFormatProvider^ provider )
   {
      
      // The Double conversion rounds UInt64.MaxValue to an invalid
      // UInt64 value, so the following limit must be used.
      return Convert::ToUInt64( CalcNLimitAverage( 0, 18446744073709550000.0, provider ) );
   }

   virtual Object^ ToType( Type^ conversionType, IFormatProvider^ provider )
   {
      return Convert::ChangeType( Average( GetAverageInfo( provider )->TypeOfAverage ), conversionType );
   }

   virtual String^ ToString( IFormatProvider^ provider )
   {
      AverageType avgType = GetAverageInfo( provider )->TypeOfAverage;
      return String::Format( "( {0}: {1:G10} )", avgType, Average( avgType ) );
   }

};


// Display a DataSet with three different format providers.
void DisplayDataSet( DataSet^ ds )
{
   IFormatProvider^ null = nullptr;
   String^ fmt = "{0,-12}{1,20}{2,20}{3,20}";
   AverageInfo^ median = gcnew AverageInfo( AverageType::Median );
   AverageInfo^ geMean = gcnew AverageInfo( AverageType::GeometricMean );
   
   // Display the dataset elements.
   if ( ds->Count > 0 )
   {
      Console::Write( "\nDataSet: [{0}", ds->Item[ 0 ] );
      for ( int iX = 1; iX < ds->Count; iX++ )
         Console::Write( ", {0}", ds->Item[ iX ] );
      Console::WriteLine( "]\n" );
   }

   Console::WriteLine( fmt, "Convert::", "Default", "Geometric Mean", "Median" );
   Console::WriteLine( fmt, "---------", "-------", "--------------", "------" );
   Console::WriteLine( fmt, "ToBoolean", Convert::ToBoolean( ds, null ), Convert::ToBoolean( ds, geMean ), Convert::ToBoolean( ds, median ) );
   Console::WriteLine( fmt, "ToByte", Convert::ToByte( ds, null ), Convert::ToByte( ds, geMean ), Convert::ToByte( ds, median ) );
   Console::WriteLine( fmt, "ToChar", Convert::ToChar( ds, null ), Convert::ToChar( ds, geMean ), Convert::ToChar( ds, median ) );
   Console::WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}"
   "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}", "ToDateTime", Convert::ToDateTime( ds, null ), Convert::ToDateTime( ds, geMean ), Convert::ToDateTime( ds, median ) );
   Console::WriteLine( fmt, "ToDecimal", Convert::ToDecimal( ds, null ), Convert::ToDecimal( ds, geMean ), Convert::ToDecimal( ds, median ) );
   Console::WriteLine( fmt, "ToDouble", Convert::ToDouble( ds, null ), Convert::ToDouble( ds, geMean ), Convert::ToDouble( ds, median ) );
   Console::WriteLine( fmt, "ToInt16", Convert::ToInt16( ds, null ), Convert::ToInt16( ds, geMean ), Convert::ToInt16( ds, median ) );
   Console::WriteLine( fmt, "ToInt32", Convert::ToInt32( ds, null ), Convert::ToInt32( ds, geMean ), Convert::ToInt32( ds, median ) );
   Console::WriteLine( fmt, "ToInt64", Convert::ToInt64( ds, null ), Convert::ToInt64( ds, geMean ), Convert::ToInt64( ds, median ) );
   Console::WriteLine( fmt, "ToSByte", Convert::ToSByte( ds, null ), Convert::ToSByte( ds, geMean ), Convert::ToSByte( ds, median ) );
   Console::WriteLine( fmt, "ToSingle", Convert::ToSingle( ds, null ), Convert::ToSingle( ds, geMean ), Convert::ToSingle( ds, median ) );
   Console::WriteLine( fmt, "ToUInt16", Convert::ToUInt16( ds, null ), Convert::ToUInt16( ds, geMean ), Convert::ToUInt16( ds, median ) );
   Console::WriteLine( fmt, "ToUInt32", Convert::ToUInt32( ds, null ), Convert::ToUInt32( ds, geMean ), Convert::ToUInt32( ds, median ) );
   Console::WriteLine( fmt, "ToUInt64", Convert::ToUInt64( ds, null ), Convert::ToUInt64( ds, geMean ), Convert::ToUInt64( ds, median ) );
}

int main()
{
   Console::WriteLine( "This example of the "
   "Convert::To<Type>( Object*, IFormatProvider* ) methods "
   "\ngenerates the following output. The example "
   "displays the values \nreturned by the methods, "
   "using several IFormatProvider objects.\n" );
   
   // To call a [ParamArray] method in C++, you cannot just
   // list the parameters, you need to build an array.
   array<Double>^dataElem = gcnew array<Double>(6);
   dataElem[ 0 ] = 10.5;
   dataElem[ 1 ] = 22.2;
   dataElem[ 2 ] = 45.9;
   dataElem[ 3 ] = 88.7;
   dataElem[ 4 ] = 156.05;
   dataElem[ 5 ] = 297.6;
   DataSet^ ds1 = gcnew DataSet( dataElem );
   DisplayDataSet( ds1 );
   dataElem = gcnew array<Double>(5);
   dataElem[ 0 ] = 359999.95;
   dataElem[ 1 ] = 425000;
   dataElem[ 2 ] = 499999.5;
   dataElem[ 3 ] = 775000;
   dataElem[ 4 ] = 1695000;
   DataSet^ ds2 = gcnew DataSet( dataElem );
   DisplayDataSet( ds2 );
}

/*
This example of the Convert::To<Type>( Object*, IFormatProvider* ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.

DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]

Convert::                Default      Geometric Mean              Median
---------                -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       103                  59                  67
ToChar                         g                   ;                   C
ToDateTime   2003-05-13 15:30:23 2003-05-13 15:29:39 2003-05-13 15:29:47
ToDecimal       103.491666666667    59.4332135445164                67.3
ToDouble        103.491666666667    59.4332135445164                67.3
ToInt16                      103                  59                  67
ToInt32                      103                  59                  67
ToInt64                      103                  59                  67
ToSByte                      103                  59                  67
ToSingle                103.4917            59.43321                67.3
ToUInt16                     103                  59                  67
ToUInt32                     103                  59                  67
ToUInt64                     103                  59                  67

DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]

Convert::                Default      Geometric Mean              Median
---------                -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       255                 255                 255
ToChar                         ?                   ?                   ?
ToDateTime   2003-05-22 08:05:19 2003-05-20 22:54:57 2003-05-19 10:21:59
ToDecimal              750999.89    631577.237188435            499999.5
ToDouble               750999.89    631577.237188435            499999.5
ToInt16                    32767               32767               32767
ToInt32                   751000              631577              500000
ToInt64                   751000              631577              500000
ToSByte                      127                 127                 127
ToSingle                750999.9            631577.3            499999.5
ToUInt16                   65535               65535               65535
ToUInt32                  751000              631577              500000
ToUInt64                  751000              631577              500000
*/

using System;
using System.Collections;

// Define the types of averaging available in the class
// implementing IConvertible.
public enum AverageType : short
{
    None = 0,
    GeometricMean = 1,
    ArithmeticMean = 2,
    Median = 3
};

// Pass an instance of this class to methods that require an
// IFormatProvider. The class instance determines the type of
// average to calculate.
public class AverageInfo : IFormatProvider
{
    protected AverageType AvgType;

    // Specify the type of averaging in the constructor.
    public AverageInfo( AverageType avgType )
    {
        this.AvgType = avgType;
    }

    // This method returns a reference to the containing object
    // if an object of AverageInfo type is requested.
    public object GetFormat( Type argType )
    {
        if ( argType == typeof( AverageInfo ) )
            return this;
        else
            return null;
    }

    // Use this property to set or get the type of averaging.
    public AverageType TypeOfAverage
    {
        get { return this.AvgType; }
        set { this.AvgType = value; }
    }
}

// This class encapsulates an array of double values and implements
// the IConvertible interface. Most of the IConvertible methods
// return an average of the array elements in one of three types:
// arithmetic mean, geometric mean, or median.
public class DataSet : IConvertible
{
    protected ArrayList     data;
    protected AverageInfo   defaultProvider;

    // Construct the object and add an initial list of values.
    // Create a default format provider.
    public DataSet( params double[ ] values )
    {
        data = new ArrayList( values );
        defaultProvider =
            new AverageInfo( AverageType.ArithmeticMean );
    }

    // Add additional values with this method.
    public int Add( double value )
    {
        data.Add( value );
        return data.Count;
    }

    // Get, set, and add values with this indexer property.
    public double this[ int index ]
    {
        get
        {
            if( index >= 0 && index < data.Count )
                return (double)data[ index ];
            else
                throw new InvalidOperationException(
                    "[DataSet.get] Index out of range." );
        }
        set
        {
            if( index >= 0 && index < data.Count )
                data[ index ] = value;

            else if( index == data.Count )
                data.Add( value );
            else
                throw new InvalidOperationException(
                    "[DataSet.set] Index out of range." );
        }
    }

    // This property returns the number of elements in the object.
    public int Count
    {
        get { return data.Count; }
    }

    // This method calculates the average of the object's elements.
    protected double Average( AverageType avgType )
    {
        double  SumProd;

        if( data.Count == 0 )
            return 0.0;

        switch( avgType )
        {
            case AverageType.GeometricMean:

                SumProd = 1.0;
                for( int Index = 0; Index < data.Count; Index++ )
                    SumProd *= (double)data[ Index ];

                // This calculation will not fail with negative
                // elements.
                return Math.Sign( SumProd ) * Math.Pow(
                    Math.Abs( SumProd ), 1.0 / data.Count );

            case AverageType.ArithmeticMean:

                SumProd = 0.0;
                for( int Index = 0; Index < data.Count; Index++ )
                    SumProd += (double)data[ Index ];

                return SumProd / data.Count;

            case AverageType.Median:

                if( data.Count % 2 == 0 )
                    return ( (double)data[ data.Count / 2 ] +
                        (double)data[ data.Count / 2 - 1 ] ) / 2.0;
                else
                    return (double)data[ data.Count / 2 ];

            default:
                return 0.0;
        }
    }

    // Get the AverageInfo object from the caller's format provider,
    // or use the local default.
    protected AverageInfo GetAverageInfo( IFormatProvider provider )
    {
        AverageInfo avgInfo = null;

        if( provider != null )
            avgInfo = (AverageInfo)provider.GetFormat(
                typeof( AverageInfo ) );

        if ( avgInfo == null )
            return defaultProvider;
        else
            return avgInfo;
    }

    // Calculate the average and limit the range.
    protected double CalcNLimitAverage( double min, double max,
        IFormatProvider provider )
    {
        // Get the format provider and calculate the average.
        AverageInfo avgInfo = GetAverageInfo( provider );
        double avg = Average( avgInfo.TypeOfAverage );

        // Limit the range, based on the minimum and maximum values
        // for the type.
        return avg > max ? max : avg < min ? min : avg;
    }

    // The following elements are required by IConvertible.

    // None of these conversion functions throw exceptions. When
    // the data is out of range for the type, the appropriate
    // MinValue or MaxValue is used.
    public TypeCode GetTypeCode( )
    {
        return TypeCode.Object;
    }

    public bool ToBoolean( IFormatProvider provider )
    {
        // ToBoolean is false if the dataset is empty.
        if( data.Count <= 0 )
        {
            return false;
        }

        // For median averaging, ToBoolean is true if any
        // non-discarded elements are nonzero.
        else if( AverageType.Median ==
            GetAverageInfo( provider ).TypeOfAverage )
        {
            if (data.Count % 2 == 0 )
                return ( (double)data[ data.Count / 2 ] != 0.0 ||
                    (double)data[ data.Count / 2 - 1 ] != 0.0 );
            else
                return (double)data[ data.Count / 2 ] != 0.0;
        }

        // For arithmetic or geometric mean averaging, ToBoolean is
        // true if any element of the dataset is nonzero.
        else
        {
            for( int Index = 0; Index < data.Count; Index++ )
                if( (double)data[ Index ] != 0.0 )
                    return true;
            return false;
        }
    }

    public byte ToByte( IFormatProvider provider )
    {
        return Convert.ToByte( CalcNLimitAverage(
            Byte.MinValue, Byte.MaxValue, provider ) );
    }

    public char ToChar( IFormatProvider provider )
    {
        return Convert.ToChar( Convert.ToUInt16( CalcNLimitAverage(
            Char.MinValue, Char.MaxValue, provider ) ) );
    }

    // Convert to DateTime by adding the calculated average as
    // seconds to the current date and time. A valid DateTime is
    // always returned.
    public DateTime ToDateTime( IFormatProvider provider )
    {
        double seconds =
            Average( GetAverageInfo( provider ).TypeOfAverage );
        try
        {
            return DateTime.Now.AddSeconds( seconds );
        }
        catch( ArgumentOutOfRangeException )
        {
            return seconds < 0.0 ? DateTime.MinValue : DateTime.MaxValue;
        }
    }

    public decimal ToDecimal( IFormatProvider provider )
    {
        // The Double conversion rounds Decimal.MinValue and
        // Decimal.MaxValue to invalid Decimal values, so the
        // following limits must be used.
        return Convert.ToDecimal( CalcNLimitAverage(
            -79228162514264330000000000000.0,
            79228162514264330000000000000.0, provider ) );
    }

    public double ToDouble( IFormatProvider provider )
    {
        return Average( GetAverageInfo(provider).TypeOfAverage );
    }

    public short ToInt16( IFormatProvider provider )
    {
        return Convert.ToInt16( CalcNLimitAverage(
            Int16.MinValue, Int16.MaxValue, provider ) );
    }

    public int ToInt32( IFormatProvider provider )
    {
        return Convert.ToInt32( CalcNLimitAverage(
            Int32.MinValue, Int32.MaxValue, provider ) );
    }

    public long ToInt64( IFormatProvider provider )
    {
        // The Double conversion rounds Int64.MinValue and
        // Int64.MaxValue to invalid Int64 values, so the following
        // limits must be used.
        return Convert.ToInt64( CalcNLimitAverage(
            -9223372036854775000, 9223372036854775000, provider ) );
    }

    public SByte ToSByte( IFormatProvider provider )
    {
        return Convert.ToSByte( CalcNLimitAverage(
            SByte.MinValue, SByte.MaxValue, provider ) );
    }

    public float ToSingle( IFormatProvider provider )
    {
        return Convert.ToSingle( CalcNLimitAverage(
            Single.MinValue, Single.MaxValue, provider ) );
    }

    public UInt16 ToUInt16( IFormatProvider provider )
    {
        return Convert.ToUInt16( CalcNLimitAverage(
            UInt16.MinValue, UInt16.MaxValue, provider ) );
    }

    public UInt32 ToUInt32( IFormatProvider provider )
    {
        return Convert.ToUInt32( CalcNLimitAverage(
            UInt32.MinValue, UInt32.MaxValue, provider ) );
    }

    public UInt64 ToUInt64( IFormatProvider provider )
    {
        // The Double conversion rounds UInt64.MaxValue to an invalid
        // UInt64 value, so the following limit must be used.
        return Convert.ToUInt64( CalcNLimitAverage(
            0, 18446744073709550000.0, provider ) );
    }

    public object ToType( Type conversionType,
        IFormatProvider provider )
    {
        return Convert.ChangeType( Average(
            GetAverageInfo( provider ).TypeOfAverage ),
            conversionType );
    }

    public string ToString( IFormatProvider provider )
    {
        AverageType avgType = GetAverageInfo( provider ).TypeOfAverage;
        return String.Format( "( {0}: {1:G10} )", avgType,
            Average( avgType ) );
    }
}

class IConvertibleProviderDemo
{
    // Display a DataSet with three different format providers.
    public static void DisplayDataSet( DataSet ds )
    {
        string      fmt    = "{0,-12}{1,20}{2,20}{3,20}";
        AverageInfo median = new AverageInfo( AverageType.Median );
        AverageInfo geMean =
            new AverageInfo( AverageType.GeometricMean );

         // Display the dataset elements.
        if( ds.Count > 0 )
        {
            Console.Write( "\nDataSet: [{0}", ds[ 0 ] );
            for( int iX = 1; iX < ds.Count; iX++ )
                Console.Write( ", {0}", ds[ iX ] );
            Console.WriteLine( "]\n" );
        }

        Console.WriteLine( fmt, "Convert.", "Default",
            "Geometric Mean", "Median");
        Console.WriteLine( fmt, "--------", "-------",
            "--------------", "------");
        Console.WriteLine( fmt, "ToBoolean",
            Convert.ToBoolean( ds, null ),
            Convert.ToBoolean( ds, geMean ),
            Convert.ToBoolean( ds, median ) );
        Console.WriteLine( fmt, "ToByte",
            Convert.ToByte( ds, null ),
            Convert.ToByte( ds, geMean ),
            Convert.ToByte( ds, median ) );
        Console.WriteLine( fmt, "ToChar",
            Convert.ToChar( ds, null ),
            Convert.ToChar( ds, geMean ),
            Convert.ToChar( ds, median ) );
        Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}" +
            "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}",
            "ToDateTime", Convert.ToDateTime( ds, null ),
            Convert.ToDateTime( ds, geMean ),
            Convert.ToDateTime( ds, median ) );
        Console.WriteLine( fmt, "ToDecimal",
            Convert.ToDecimal( ds, null ),
            Convert.ToDecimal( ds, geMean ),
            Convert.ToDecimal( ds, median ) );
        Console.WriteLine( fmt, "ToDouble",
            Convert.ToDouble( ds, null ),
            Convert.ToDouble( ds, geMean ),
            Convert.ToDouble( ds, median ) );
        Console.WriteLine( fmt, "ToInt16",
            Convert.ToInt16( ds, null ),
            Convert.ToInt16( ds, geMean ),
            Convert.ToInt16( ds, median ) );
        Console.WriteLine( fmt, "ToInt32",
            Convert.ToInt32( ds, null ),
            Convert.ToInt32( ds, geMean ),
            Convert.ToInt32( ds, median ) );
        Console.WriteLine( fmt, "ToInt64",
            Convert.ToInt64( ds, null ),
            Convert.ToInt64( ds, geMean ),
            Convert.ToInt64( ds, median ) );
        Console.WriteLine( fmt, "ToSByte",
            Convert.ToSByte( ds, null ),
            Convert.ToSByte( ds, geMean ),
            Convert.ToSByte( ds, median ) );
        Console.WriteLine( fmt, "ToSingle",
            Convert.ToSingle( ds, null ),
            Convert.ToSingle( ds, geMean ),
            Convert.ToSingle( ds, median ) );
        Console.WriteLine( fmt, "ToUInt16",
            Convert.ToUInt16( ds, null ),
            Convert.ToUInt16( ds, geMean ),
            Convert.ToUInt16( ds, median ) );
        Console.WriteLine( fmt, "ToUInt32",
            Convert.ToUInt32( ds, null ),
            Convert.ToUInt32( ds, geMean ),
            Convert.ToUInt32( ds, median ) );
        Console.WriteLine( fmt, "ToUInt64",
            Convert.ToUInt64( ds, null ),
            Convert.ToUInt64( ds, geMean ),
            Convert.ToUInt64( ds, median ) );
    }

    public static void Main( )
    {
        Console.WriteLine( "This example of " +
            "the Convert.To<Type>( object, IFormatProvider ) methods " +
            "\ngenerates the following output. The example " +
            "displays the values \nreturned by the methods, " +
            "using several IFormatProvider objects.\n" );

        DataSet ds1 = new DataSet(
            10.5, 22.2, 45.9, 88.7, 156.05, 297.6 );
        DisplayDataSet( ds1 );

        DataSet ds2 = new DataSet(
            359999.95, 425000, 499999.5, 775000, 1695000 );
        DisplayDataSet( ds2 );
    }
}

/*
This example of the Convert.To<Type>( object, IFormatProvider ) methods
generates the following output. The example displays the values
returned by the methods, using several IFormatProvider objects.

DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       103                  59                  67
ToChar                         g                   ;                   C
ToDateTime   2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
ToDecimal       103.491666666667    59.4332135445164                67.3
ToDouble        103.491666666667    59.4332135445164                67.3
ToInt16                      103                  59                  67
ToInt32                      103                  59                  67
ToInt64                      103                  59                  67
ToSByte                      103                  59                  67
ToSingle                103.4917            59.43321                67.3
ToUInt16                     103                  59                  67
ToUInt32                     103                  59                  67
ToUInt64                     103                  59                  67

DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]

Convert.                 Default      Geometric Mean              Median
--------                 -------      --------------              ------
ToBoolean                   True                True                True
ToByte                       255                 255                 255
ToChar                         ?                   ?                   ?
ToDateTime   2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
ToDecimal              750999.89    631577.237188435            499999.5
ToDouble               750999.89    631577.237188435            499999.5
ToInt16                    32767               32767               32767
ToInt32                   751000              631577              500000
ToInt64                   751000              631577              500000
ToSByte                      127                 127                 127
ToSingle                750999.9            631577.3            499999.5
ToUInt16                   65535               65535               65535
ToUInt32                  751000              631577              500000
ToUInt64                  751000              631577              500000
*/

open System
open System.Collections

// Define the types of averaging available in the class
// implementing IConvertible.
type AverageType =
    | None = 0s
    | GeometricMean = 1s
    | ArithmeticMean = 2s
    | Median = 3s

// Pass an instance of this class to methods that require an
// IFormatProvider. The class instance determines the type of
// average to calculate.
[<AllowNullLiteral>]
type AverageInfo(avgType: AverageType) =
    // Use this property to set or get the type of averaging.
    member val TypeOfAverage = avgType with get, set 
    
    interface IFormatProvider with
        // This method returns a reference to the containing object
        // if an object of AverageInfo type is requested.
        member this.GetFormat(argType: Type) =
            if argType = typeof<AverageInfo> then
                this
            else
                null

// This class encapsulates an array of double values and implements
// the IConvertible interface. Most of the IConvertible methods
// an average of the array elements in one of three types:
// arithmetic mean, geometric mean, or median.
type DataSet([<ParamArray>] values: double[]) =
    let data = ResizeArray values
    let defaultProvider =
        AverageInfo AverageType.ArithmeticMean

    // Add additional values with this method.
    member _.Add(value: double) =
        data.Add value
        data.Count

    // Get, set, and add values with this indexer property.
    member _.Item
        with get (index) =
            if index >= 0 && index < data.Count then
                data[index]
            else
                raise (InvalidOperationException "[DataSet.get] Index out of range.")
        and set index value =
            if index >= 0 && index < data.Count then
                data[index] <- value
            elif index = data.Count then
                data.Add value
            else
                raise (InvalidOperationException "[DataSet.set] Index out of range.")

    // This property returns the number of elements in the object.
    member _.Count =
        data.Count

    // This method calculates the average of the object's elements.
    member _.Average(avgType: AverageType) =
        if data.Count = 0 then
            0.0
        else
            match avgType with
            | AverageType.GeometricMean ->
                let sumProd =
                    Seq.reduce ( * ) data
                
                // This calculation will not fail with negative
                // elements.
                (sign sumProd |> float) * Math.Pow(abs sumProd, 1.0 / (float data.Count))

            | AverageType.ArithmeticMean ->
                Seq.average data

            | AverageType.Median ->
                if data.Count % 2 = 0 then
                    (data[data.Count / 2] + data[data.Count / 2 - 1]) / 2.0
                else
                    data[ data.Count / 2]
            | _ ->
                0.0

    // Get the AverageInfo object from the caller's format provider,
    // or use the local default.
    member _.GetAverageInfo(provider: IFormatProvider) =
        let avgInfo =
            if provider <> null then
                provider.GetFormat typeof<AverageInfo> :?> AverageInfo
            else 
                null

        if avgInfo = null then
            defaultProvider
        else
            avgInfo

    // Calculate the average and limit the range.
    member this.CalcNLimitAverage(min: double, max: double, provider: IFormatProvider) =
        // Get the format provider and calculate the average.
        let avgInfo = this.GetAverageInfo provider
        let avg = this.Average avgInfo.TypeOfAverage

        // Limit the range, based on the minimum and maximum values
        // for the type.
        if avg > max then max elif avg < min then min else avg

    // The following elements are required by IConvertible.
    interface IConvertible with
        // None of these conversion functions throw exceptions. When
        // the data is out of range for the type, the appropriate
        // MinValue or MaxValue is used.
        member _.GetTypeCode() =
            TypeCode.Object

        member this.ToBoolean(provider: IFormatProvider) =
            // ToBoolean is false if the dataset is empty.
            if data.Count <= 0 then
                false

            // For median averaging, ToBoolean is true if any
            // non-discarded elements are nonzero.
            elif AverageType.Median = this.GetAverageInfo(provider).TypeOfAverage then
                if data.Count % 2 = 0 then
                    (data[data.Count / 2] <> 0.0 || data[data.Count / 2 - 1] <> 0.0)
                else
                    data[data.Count / 2] <> 0.0

            // For arithmetic or geometric mean averaging, ToBoolean is
            // true if any element of the dataset is nonzero.
            else
                Seq.exists (fun x -> x <> 0.0) data

        member this.ToByte(provider: IFormatProvider) =
            Convert.ToByte(this.CalcNLimitAverage(float Byte.MinValue, float Byte.MaxValue, provider) )

        member this.ToChar(provider: IFormatProvider) =
            Convert.ToChar(Convert.ToUInt16(this.CalcNLimitAverage(float Char.MinValue, float Char.MaxValue, provider) ) )

        // Convert to DateTime by adding the calculated average as
        // seconds to the current date and time. A valid DateTime is
        // always returned.
        member this.ToDateTime(provider: IFormatProvider) =
            let seconds = this.Average(this.GetAverageInfo(provider).TypeOfAverage)
            try
                DateTime.Now.AddSeconds seconds
            with :? ArgumentOutOfRangeException ->
                if seconds < 0.0 then DateTime.MinValue else DateTime.MaxValue

        member this.ToDecimal(provider: IFormatProvider) =
            // The Double conversion rounds Decimal.MinValue and
            // Decimal.MaxValue to invalid Decimal values, so the
            // following limits must be used.
            Convert.ToDecimal(this.CalcNLimitAverage(-79228162514264330000000000000.0, 79228162514264330000000000000.0, provider) )

        member this.ToDouble(provider: IFormatProvider) =
            this.Average(this.GetAverageInfo(provider).TypeOfAverage)

        member this.ToInt16(provider: IFormatProvider) =
            Convert.ToInt16(this.CalcNLimitAverage(float Int16.MinValue, float Int16.MaxValue, provider) )

        member this.ToInt32(provider: IFormatProvider) =
            Convert.ToInt32(this.CalcNLimitAverage(Int32.MinValue, Int32.MaxValue, provider) )

        member this.ToInt64(provider: IFormatProvider) =
            // The Double conversion rounds Int64.MinValue and
            // Int64.MaxValue to invalid Int64 values, so the following
            // limits must be used.
            Convert.ToInt64(this.CalcNLimitAverage(-9223372036854775000., 9223372036854775000., provider) )

        member this.ToSByte(provider: IFormatProvider) =
            Convert.ToSByte(this.CalcNLimitAverage(float SByte.MinValue, float SByte.MaxValue, provider) )

        member this.ToSingle(provider: IFormatProvider) =
            Convert.ToSingle(this.CalcNLimitAverage(float Single.MinValue, float Single.MaxValue, provider) )

        member this.ToUInt16(provider: IFormatProvider) =
            Convert.ToUInt16(this.CalcNLimitAverage(float UInt16.MinValue, float UInt16.MaxValue, provider) )

        member this.ToUInt32(provider: IFormatProvider) =
            Convert.ToUInt32(this.CalcNLimitAverage(float UInt32.MinValue, float UInt32.MaxValue, provider) )

        member this.ToUInt64(provider: IFormatProvider) =
            // The Double conversion rounds UInt64.MaxValue to an invalid
            // UInt64 value, so the following limit must be used.
            Convert.ToUInt64(this.CalcNLimitAverage(0, 18446744073709550000.0, provider) )

        member this.ToType(conversionType: Type, provider: IFormatProvider) =
            Convert.ChangeType(this.Average(this.GetAverageInfo(provider).TypeOfAverage), conversionType)

        member this.ToString(provider: IFormatProvider) =
            let avgType = this.GetAverageInfo(provider).TypeOfAverage
            $"( {avgType}: {this.Average avgType:G10} )"                

// Display a DataSet with three different format providers.
let displayDataSet (ds: DataSet) =
    let fmt obj1 obj2 obj3 obj4 = printfn $"{obj1,-12}{obj2,20}{obj3,20}{obj4,20}"
    let median = AverageInfo AverageType.Median
    let geMean =
        AverageInfo AverageType.GeometricMean

    // Display the dataset elements.
    if ds.Count > 0 then
        printf $"\nDataSet: [{ds[0]}"
        for i = 1 to ds.Count - 1 do
            printf $", {ds[i]}"
        printfn "]\n"

    fmt "Convert." "Default" "Geometric Mean" "Median"
    fmt "--------" "-------" "--------------" "------"
    fmt "ToBoolean"
        (Convert.ToBoolean(ds, null))
        (Convert.ToBoolean(ds, geMean))
        (Convert.ToBoolean(ds, median))
    fmt "ToByte"
        (Convert.ToByte(ds, null))
        (Convert.ToByte(ds, geMean))
        (Convert.ToByte(ds, median))
    fmt "ToChar"
        (Convert.ToChar(ds, null))
        (Convert.ToChar(ds, geMean))
        (Convert.ToChar(ds, median))
    printfn $"""{"ToDateTime",-12}{Convert.ToDateTime(ds, null).ToString "20:yyyy-MM-dd HH:mm:ss"}{Convert.ToDateTime(ds, geMean).ToString "20:yyyy-MM-dd HH:mm:ss"}{Convert.ToDateTime(ds, median).ToString "20:yyyy-MM-dd HH:mm:ss"}"""

    fmt "ToDecimal"
        (Convert.ToDecimal(ds, null))
        (Convert.ToDecimal(ds, geMean))
        (Convert.ToDecimal(ds, median))
    fmt "ToDouble"
        (Convert.ToDouble(ds, null))
        (Convert.ToDouble(ds, geMean))
        (Convert.ToDouble(ds, median))
    fmt "ToInt16"
        (Convert.ToInt16(ds, null))
        (Convert.ToInt16(ds, geMean))
        (Convert.ToInt16(ds, median))
    fmt "ToInt32"
        (Convert.ToInt32(ds, null))
        (Convert.ToInt32(ds, geMean))
        (Convert.ToInt32(ds, median))
    fmt "ToInt64"
        (Convert.ToInt64(ds, null))
        (Convert.ToInt64(ds, geMean))
        (Convert.ToInt64(ds, median))
    fmt "ToSByte"
        (Convert.ToSByte(ds, null))
        (Convert.ToSByte(ds, geMean))
        (Convert.ToSByte(ds, median))
    fmt "ToSingle"
        (Convert.ToSingle(ds, null))
        (Convert.ToSingle(ds, geMean))
        (Convert.ToSingle(ds, median))
    fmt "ToUInt16"
        (Convert.ToUInt16(ds, null))
        (Convert.ToUInt16(ds, geMean))
        (Convert.ToUInt16(ds, median))
    fmt "ToUInt32"
        (Convert.ToUInt32(ds, null))
        (Convert.ToUInt32(ds, geMean))
        (Convert.ToUInt32(ds, median))
    fmt "ToUInt64"
        (Convert.ToUInt64(ds, null))
        (Convert.ToUInt64(ds, geMean))
        (Convert.ToUInt64(ds, median))

printfn
    """This example of the Convert.To<Type>( object, IFormatprovider) methods 
generates the following output. The example displays the values 
returned by the methods, using several IFormatProvider objects.
"""

let ds1 = DataSet(10.5, 22.2, 45.9, 88.7, 156.05, 297.6)
displayDataSet ds1

let ds2 = DataSet(359999.95, 425000, 499999.5, 775000, 1695000)
displayDataSet ds2

// This example of the Convert.To<Type>( object, IFormatprovider) methods
// generates the following output. The example displays the values
// returned by the methods, using several IFormatProvider objects.
//
// DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
//
// Convert.                 Default      Geometric Mean              Median
// --------                 -------      --------------              ------
// ToBoolean                   True                True                True
// ToByte                       103                  59                  67
// ToChar                         g                   ;                   C
// ToDateTime   2003-05-13 15:04:12 2003-05-13 15:03:28 2003-05-13 15:03:35
// ToDecimal       103.491666666667    59.4332135445164                67.3
// ToDouble        103.491666666667    59.4332135445164                67.3
// ToInt16                      103                  59                  67
// ToInt32                      103                  59                  67
// ToInt64                      103                  59                  67
// ToSByte                      103                  59                  67
// ToSingle                103.4917            59.43321                67.3
// ToUInt16                     103                  59                  67
// ToUInt32                     103                  59                  67
// ToUInt64                     103                  59                  67
//
// DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
//
// Convert.                 Default      Geometric Mean              Median
// --------                 -------      --------------              ------
// ToBoolean                   True                True                True
// ToByte                       255                 255                 255
// ToChar                         ?                   ?                   ?
// ToDateTime   2003-05-22 07:39:08 2003-05-20 22:28:45 2003-05-19 09:55:48
// ToDecimal              750999.89    631577.237188435            499999.5
// ToDouble               750999.89    631577.237188435            499999.5
// ToInt16                    32767               32767               32767
// ToInt32                   751000              631577              500000
// ToInt64                   751000              631577              500000
// ToSByte                      127                 127                 127
// ToSingle                750999.9            631577.3            499999.5
// ToUInt16                   65535               65535               65535
// ToUInt32                  751000              631577              500000
// ToUInt64                  751000              631577              500000

Imports System.Collections

Module IConvertibleProviderDemo

    ' Define the types of averaging available in the class 
    ' implementing IConvertible.
    Enum AverageType as Short
        None = 0
        GeometricMean = 1
        ArithmeticMean = 2
        Median = 3
    End Enum

    ' Pass an instance of this class to methods that require an 
    ' IFormatProvider. The class instance determines the type of 
    ' average to calculate.
    Public Class AverageInfo
        Implements IFormatProvider

        Protected  AvgType      As AverageType

        ' Specify the type of averaging in the constructor.
        Public Sub New( avgType As AverageType )
            Me.AvgType = avgType
        End Sub

        ' This method returns a reference to the containing object 
        ' if an object of AverageInfo type is requested. 
        Public Function GetFormat( argType As Type ) As Object _
            Implements IFormatProvider.GetFormat

            If argType Is GetType( AverageInfo ) Then
                Return Me
            Else
                Return Nothing
            End If
        End Function 

        ' Use this property to set or get the type of averaging.
        Public Property TypeOfAverage( ) As AverageType
            Get
                Return Me.AvgType
            End Get
            Set( ByVal value as AverageType )
                Me.AvgType = value
            End Set
        End Property
    End Class 

    ' This class encapsulates an array of Double values and implements 
    ' the IConvertible interface. Most of the IConvertible methods 
    ' return an average of the array elements in one of three types: 
    ' arithmetic mean, geometric mean, or median. 
    Public Class DataSet
        Implements IConvertible

        Protected data              As ArrayList
        Protected defaultProvider   As AverageInfo
           
        ' Construct the object and add an initial list of values.
        ' Create a default format provider.
        Public Sub New( ParamArray values( ) As Double )
            data = New ArrayList( values )
            defaultProvider = New AverageInfo( _
                AverageType.ArithmeticMean )  
        End Sub
           
        ' Add additional values with this method.
        Public Function Add( value As Double ) As Integer
            data.Add( value )
            Return data.Count
        End Function
           
        ' Get, set, and add values with this indexer property.
        Default Public Property Item(index As Integer) As Double
            Get
                If index >= 0 AndAlso index < data.Count Then
                    Return System.Convert.ToDouble( data( index ) )
                Else
                    Throw New InvalidOperationException( _
                        "[DataSet.get] Index out of range." )
                End If
            End Get
            Set
                If index >= 0 AndAlso index < data.Count Then
                    data( index ) = value
                 
                ElseIf index = data.Count Then
                    data.Add( value )
                Else
                    Throw New InvalidOperationException( _
                        "[DataSet.set] Index out of range." )
                End If
            End Set
        End Property
          
        ' This property returns the number of elements in the object.
        Public ReadOnly Property Count( ) As Integer
            Get
                Return data.Count
            End Get
        End Property

        ' This method calculates the average of the object's elements.
        Protected Function Average( ByVal avgType As AverageType ) As Double

            Dim SumProd As Double 
            Dim Index   As Integer

            If data.Count = 0 Then Return 0.0

            Select Case avgType
                
                Case AverageType.GeometricMean

                    SumProd = 1.0
                    For Index = 0 To data.Count - 1
                        SumProd *= data( Index )
                    Next Index
                    
                    ' This calculation will not fail with negative 
                    ' elements.
                    Return Math.Sign( SumProd ) * Math.Pow( _
                        Math.Abs( SumProd ), 1.0 / data.Count )

                Case AverageType.ArithmeticMean

                    SumProd = 0.0
                    For Index = 0 To data.Count - 1
                        SumProd += data( Index )
                    Next Index

                    Return SumProd / data.Count 

                Case AverageType.Median

                    If data.Count Mod 2 = 0 Then
                        Return ( data( data.Count \ 2 ) + _
                            data( data.Count \ 2 - 1 ) ) / 2.0
                    Else
                        Return data( data.Count \ 2 ) 
                    End If
            End Select
        End Function

        ' Get the AverageInfo object from the caller's format 
        ' provider, or use the local default.
        Protected Function GetAverageInfo( _
            provider As IFormatProvider ) As AverageInfo

            Dim avgInfo As AverageInfo = Nothing

            If Not provider Is Nothing Then
                avgInfo = provider.GetFormat( GetType( AverageInfo ) )
            End If

            Return IIf( avgInfo Is Nothing, defaultProvider, avgInfo )
            
        End Function           

        ' Calculate the average and limit the range.
        Protected Function CalcNLimitAverage( min As Double, _
            max As Double, provider as IFormatProvider ) As Double

            ' Get the format provider and calculate the average.
            Dim avgInfo As AverageInfo = GetAverageInfo( provider )
            Dim avg As Double = Average( avgInfo.TypeOfAverage )

            ' Limit the range, based on the minimum and maximum values 
            ' for the type.
            Return IIf( avg > max, max, IIf( avg < min, min, avg ) )

        End Function

        ' The following elements are required by IConvertible.

        ' None of these conversion functions throw exceptions. When
        ' the data is out of range for the type, the appropriate
        ' MinValue or MaxValue is used.
        Public Function GetTypeCode( ) As TypeCode _
            Implements IConvertible.GetTypeCode
            Return TypeCode.Object
        End Function

        Function ToBoolean( ByVal provider As IFormatProvider ) As _
            Boolean Implements IConvertible.ToBoolean

            ' ToBoolean is false if the dataset is empty.
            If data.Count <= 0 Then
                Return False

            ' For median averaging, ToBoolean is true if any 
            ' non-discarded elements are nonzero.
            ElseIf AverageType.Median = _
                GetAverageInfo( provider ).TypeOfAverage Then

                If data.Count Mod 2 = 0 Then
                    Return ( data( data.Count \ 2 ) <> 0.0 Or _
                        data( data.Count \ 2 - 1 ) <> 0.0 )
                Else
                    Return data( data.Count \ 2 ) <> 0.0
                End If

            ' For arithmetic or geometric mean averaging, ToBoolean is 
            ' true if any element of the dataset is nonzero.  
            Else
                Dim Index As Integer
                For Index = 0 To data.Count - 1
                    If data( Index ) <> 0.0 Then Return True
                Next Index
                Return False
            End If
        End Function

        Function ToByte( ByVal provider As IFormatProvider ) As Byte _
            Implements IConvertible.ToByte
            Return Convert.ToByte( CalcNLimitAverage( _
                Byte.MinValue, Byte.MaxValue, provider ) )
        End Function

        Function ToChar( ByVal provider As IFormatProvider ) As Char _
            Implements IConvertible.ToChar
            Return Convert.ToChar( Convert.ToUInt16( _
                CalcNLimitAverage( 0.0, &HFFFF, provider ) ) )
        End Function

        ' Convert to DateTime by adding the calculated average as 
        ' seconds to the current date and time. A valid DateTime is 
        ' always returned.
        Function ToDateTime( ByVal provider As IFormatProvider ) As _
            DateTime Implements IConvertible.ToDateTime
            Dim seconds As Double = Average( _
                GetAverageInfo( provider ).TypeOfAverage )
            Try
                Return DateTime.Now.AddSeconds( seconds )
            Catch ex As ArgumentOutOfRangeException 
                Return IIf( seconds < 0.0, DateTime.MinValue, _
                    DateTime.MaxValue )
            End Try
        End Function

        Function ToDecimal( ByVal provider As IFormatProvider ) As _
            Decimal Implements IConvertible.ToDecimal

            ' The Double conversion rounds Decimal.MinValue and
            ' Decimal.MaxValue to invalid Decimal values, so the 
            ' following limits must be used.
            Return Convert.ToDecimal( CalcNLimitAverage( _
                -79228162514264330000000000000.0, _
                79228162514264330000000000000.0, provider ) )
        End Function

        Function ToDouble( ByVal provider As IFormatProvider) As _
            Double Implements IConvertible.ToDouble
            Return Average( GetAverageInfo( provider ).TypeOfAverage )
        End Function

        Function ToInt16( ByVal provider As IFormatProvider ) As _
            Short Implements IConvertible.ToInt16
            Return Convert.ToInt16( CalcNLimitAverage( _
                Int16.MinValue, Int16.MaxValue, provider ) )
        End Function

        Function ToInt32( ByVal provider As IFormatProvider ) As _
            Integer Implements IConvertible.ToInt32
            Return Convert.ToInt32( CalcNLimitAverage( _
                Int32.MinValue, Int32.MaxValue, provider ) )
        End Function

        Function ToInt64( ByVal provider As IFormatProvider ) As Long _
            Implements IConvertible.ToInt64

            ' The Double conversion rounds Int64.MinValue and 
            ' Int64.MaxValue to invalid Long values, so the following 
            ' limits must be used.
            Return Convert.ToInt64( CalcNLimitAverage( _
                -9223372036854775000, 9223372036854775000, provider ) )
        End Function

        Function ToSByte( ByVal provider As IFormatProvider ) As _
            SByte Implements IConvertible.ToSByte

            ' SByte.MinValue and SByte.MaxValue are not defined in
            ' Visual Basic.
            Return Convert.ToSByte( CalcNLimitAverage( _
                -128, 127, provider ) )
        End Function

        Function ToSingle( ByVal provider As IFormatProvider ) As _
            Single Implements IConvertible.ToSingle
            Return Convert.ToSingle( CalcNLimitAverage( _
                Single.MinValue, Single.MaxValue, provider ) )
        End Function

        Function ToUInt16( ByVal provider As IFormatProvider ) As _
            UInt16 Implements IConvertible.ToUInt16

            ' UInt16.MinValue and UInt16.MaxValue are not defined in 
            ' Visual Basic.
            Return Convert.ToUInt16( CalcNLimitAverage( _
                0, &HFFFF, provider ) )
        End Function

        Function ToUInt32( ByVal provider As IFormatProvider ) As _
            UInt32 Implements IConvertible.ToUInt32

            ' UInt32.MinValue and UInt32.MaxValue are not defined in 
            ' Visual Basic.
            Return Convert.ToUInt32( CalcNLimitAverage( _
                0, 4294967295, provider ) )
        End Function

        Function ToUInt64( ByVal provider As IFormatProvider ) As _
            UInt64 Implements IConvertible.ToUInt64

            ' UInt64.MinValue and UInt64.MaxValue are not defined in 
            ' Visual Basic. The Double conversion would have rounded 
            ' UInt64.MaxValue, so the following limit must be used.
            Return Convert.ToUInt64( CalcNLimitAverage( _
                0, 18446744073709550000.0, provider ) )
        End Function

        Function ToType( ByVal conversionType As Type, _
            ByVal provider As IFormatProvider) As Object _
            Implements IConvertible.ToType
            Return Convert.ChangeType( Average( GetAverageInfo( _
                provider ).TypeOfAverage ), conversionType )
        End Function

        Overloads Function ToString( ByVal provider As IFormatProvider _
            ) As String Implements IConvertible.ToString
            Dim avgType as AverageType = _
                GetAverageInfo( provider ).TypeOfAverage
            Return String.Format( "( {0}: {1:G10} )", avgType, _
                Average( avgType ) )
        End Function
    End Class
   
    ' Display a DataSet with three different format providers.
    Sub DisplayDataSet( ds As DataSet )

        Dim fmt    As String      = "{0,-12}{1,20}{2,20}{3,20}"
        Dim median As AverageInfo = New AverageInfo( AverageType.Median )
        Dim geMean As AverageInfo = _
            New AverageInfo( AverageType.GeometricMean )
        Dim iX     As Integer

        ' Display the dataset elements.
        If ds.Count > 0 Then
            Console.Write( vbCrLf & "DataSet: [{0}", ds( 0 ) )
            For iX = 1 To ds.Count - 1
                Console.Write( ", {0}", ds( iX ) )
            Next iX
            Console.WriteLine( "]" & vbCrLf )
        End If

        Console.WriteLine( fmt, "Convert.", "Default", _
            "Geometric Mean", "Median" )
        Console.WriteLine( fmt, "--------", "-------", _
            "--------------", "------" )
        Console.WriteLine( fmt, "ToBoolean", _
            Convert.ToBoolean( ds, Nothing ), _
            Convert.ToBoolean( ds, geMean ), _
            Convert.ToBoolean( ds, median ) )
        Console.WriteLine( fmt, "ToByte", _
            Convert.ToByte( ds, Nothing ), _
            Convert.ToByte( ds, geMean ), _
            Convert.ToByte( ds, median ) )
        Console.WriteLine( fmt, "ToChar", _
            Convert.ToChar( ds, Nothing ), _
            Convert.ToChar( ds, geMean ), _
            Convert.ToChar( ds, median ) )
        Console.WriteLine( "{0,-12}{1,20:yyyy-MM-dd HH:mm:ss}" & _
            "{2,20:yyyy-MM-dd HH:mm:ss}{3,20:yyyy-MM-dd HH:mm:ss}", _
            "ToDateTime", Convert.ToDateTime( ds, Nothing ), _
            Convert.ToDateTime( ds, geMean ), _
            Convert.ToDateTime( ds, median ) )
        Console.WriteLine( fmt, "ToDecimal", _
            Convert.ToDecimal( ds, Nothing ), _
            Convert.ToDecimal( ds, geMean ), _
            Convert.ToDecimal( ds, median ) )
        Console.WriteLine( fmt, "ToDouble", _
            Convert.ToDouble( ds, Nothing ), _
            Convert.ToDouble( ds, geMean ), _
            Convert.ToDouble( ds, median ) )
        Console.WriteLine( fmt, "ToInt16", _
            Convert.ToInt16( ds, Nothing ), _
            Convert.ToInt16( ds, geMean ), _
            Convert.ToInt16( ds, median ) )
        Console.WriteLine( fmt, "ToInt32", _
            Convert.ToInt32( ds, Nothing ), _
            Convert.ToInt32( ds, geMean ), _
            Convert.ToInt32( ds, median ) )
        Console.WriteLine( fmt, "ToInt64", _
            Convert.ToInt64( ds, Nothing ), _
            Convert.ToInt64( ds, geMean ), _
            Convert.ToInt64( ds, median ) )
        Console.WriteLine( fmt, "ToSByte", _
            Convert.ToSByte( ds, Nothing ), _
            Convert.ToSByte( ds, geMean ), _
            Convert.ToSByte( ds, median ) )
        Console.WriteLine( fmt, "ToSingle", _
            Convert.ToSingle( ds, Nothing ), _
            Convert.ToSingle( ds, geMean ), _
            Convert.ToSingle( ds, median ) )
        Console.WriteLine( fmt, "ToUInt16", _
            Convert.ToUInt16( ds, Nothing ), _
            Convert.ToUInt16( ds, geMean ), _
            Convert.ToUInt16( ds, median ) )
        Console.WriteLine( fmt, "ToUInt32", _
            Convert.ToUInt32( ds, Nothing ), _
            Convert.ToUInt32( ds, geMean ), _
            Convert.ToUInt32( ds, median ) )
        Console.WriteLine( fmt, "ToUInt64", _
            Convert.ToUInt64( ds, Nothing ), _
            Convert.ToUInt64( ds, geMean ), _
            Convert.ToUInt64( ds, median ) )
    End Sub
   
    Sub Main( )
        Console.WriteLine( _
            "This example of the Convert.To<Type>( Object, " & _
            "IFormatProvider ) methods " & vbCrLf & "generates " & _
            "the following output. The example displays the " & _
            "values " & vbCrLf & "returned by the methods, " & _
            "using several IFormatProvider objects." & vbCrLf )
          
        Dim ds1 As New DataSet( 10.5, 22.2, 45.9, 88.7, 156.05, 297.6 )
        DisplayDataSet( ds1 )
          
        Dim ds2 As New DataSet( _
            359999.95, 425000, 499999.5, 775000, 1695000 )
        DisplayDataSet( ds2 )
    End Sub 
End Module 

' This example of the Convert.To<Type>( Object, IFormatProvider ) methods
' generates the following output. The example displays the values
' returned by the methods, using several IFormatProvider objects.
' 
' DataSet: [10.5, 22.2, 45.9, 88.7, 156.05, 297.6]
' 
' Convert.                 Default      Geometric Mean              Median
' --------                 -------      --------------              ------
' ToBoolean                   True                True                True
' ToByte                       103                  59                  67
' ToChar                         g                   ;                   C
' ToDateTime   2003-05-13 14:52:53 2003-05-13 14:52:09 2003-05-13 14:52:17
' ToDecimal       103.491666666667    59.4332135445164                67.3
' ToDouble        103.491666666667    59.4332135445164                67.3
' ToInt16                      103                  59                  67
' ToInt32                      103                  59                  67
' ToInt64                      103                  59                  67
' ToSByte                      103                  59                  67
' ToSingle                103.4917            59.43321                67.3
' ToUInt16                     103                  59                  67
' ToUInt32                     103                  59                  67
' ToUInt64                     103                  59                  67
' 
' DataSet: [359999.95, 425000, 499999.5, 775000, 1695000]
' 
' Convert.                 Default      Geometric Mean              Median
' --------                 -------      --------------              ------
' ToBoolean                   True                True                True
' ToByte                       255                 255                 255
' ToChar                         ?                   ?                   ?
' ToDateTime   2003-05-22 07:27:49 2003-05-20 22:17:27 2003-05-19 09:44:29
' ToDecimal              750999.89    631577.237188435            499999.5
' ToDouble               750999.89    631577.237188435            499999.5
' ToInt16                    32767               32767               32767
' ToInt32                   751000              631577              500000
' ToInt64                   751000              631577              500000
' ToSByte                      127                 127                 127
' ToSingle                750999.9            631577.3            499999.5
' ToUInt16                   65535               65535               65535
' ToUInt32                  751000              631577              500000
' ToUInt64                  751000              631577              500000

備註

provider 可讓使用者指定 有關 內容 value的文化特性特定轉換資訊。 基底類型會忽略 provider 參數;不過，如果 value 是實作 IConvertible 介面的使用者定義型別，可以使用 參數。

另請參閱

• Object

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::UInt64 value);

[System.CLSCompliant(false)]
public static bool ToBoolean (ulong value);

[<System.CLSCompliant(false)>]
static member ToBoolean : uint64 -> bool

Public Shared Function ToBoolean (value As ULong) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

屬性

CLSCompliantAttribute

範例

下列範例會將值的陣列 UInt64 轉換成 Boolean 值。

array<UInt64>^ numbers = gcnew array<UInt64> { UInt64::MinValue, 6121, 403890774, UInt64::MaxValue };
bool result;

for each (UInt64 number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-26:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       0                           -->  False
//       6,121                       -->  True
//       403,890,774                 -->  True
//       18,446,744,073,709,551,615  -->  True

ulong[] numbers = { UInt64.MinValue, 6121, 403890774, UInt64.MaxValue };
bool result;

foreach (ulong number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-26:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       0                           -->  False
//       6,121                       -->  True
//       403,890,774                 -->  True
//       18,446,744,073,709,551,615  -->  True

let numbers = 
    [| UInt64.MinValue; 6121uL; 403890774uL; UInt64.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-26:N0}  -->  {result}"
// The example displays the following output:
//       0                           -->  False
//       6,121                       -->  True
//       403,890,774                 -->  True
//       18,446,744,073,709,551,615  -->  True

Dim numbers() As ULong = { UInt64.MinValue, 6121, 403890774, UInt64.MaxValue }
Dim result As Boolean

For Each number As ULong In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-26:N0}  -->  {1}", number, result)
Next
' The example displays the following output:
'       0                           -->  False
'       6,121                       -->  True
'       403,890,774                 -->  True
'       18,446,744,073,709,551,615  -->  True

另請參閱

• UInt64

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::UInt32 value);

[System.CLSCompliant(false)]
public static bool ToBoolean (uint value);

[<System.CLSCompliant(false)>]
static member ToBoolean : uint32 -> bool

Public Shared Function ToBoolean (value As UInteger) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

屬性

CLSCompliantAttribute

範例

下列範例會將值的陣列 Int32 轉換成 Boolean 值。

array<UInt32>^ numbers = gcnew array<UInt32> { UInt32::MinValue, 612, 4038907, Int32::MaxValue };
bool result;
   
for each (unsigned int number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-15:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       0                -->  False
//       612              -->  True
//       4,038,907        -->  True
//       2,147,483,647    -->  True

uint[] numbers = { UInt32.MinValue, 612, 4038907, Int32.MaxValue };
bool result;

foreach (uint number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-15:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       0                -->  False
//       612              -->  True
//       4,038,907        -->  True
//       2,147,483,647    -->  True

let numbers =
    [| UInt32.MinValue; 612u; 4038907u; uint Int32.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-15:N0}  -->  {result}"
// The example displays the following output:
//       0                -->  False
//       612              -->  True
//       4,038,907        -->  True
//       2,147,483,647    -->  True

Dim numbers() As UInteger = { UInt32.MinValue, 612, 4038907, Int32.MaxValue }
Dim result As Boolean

For Each number As UInteger In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-15:N0}  -->  {1}", number, result)
Next
' The example displays the following output:
'       0                -->  False
'       612              -->  True
'       4,038,907        -->  True
'       2,147,483,647    -->  True

另請參閱

• UInt32

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::UInt16 value);

[System.CLSCompliant(false)]
public static bool ToBoolean (ushort value);

[<System.CLSCompliant(false)>]
static member ToBoolean : uint16 -> bool

Public Shared Function ToBoolean (value As UShort) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

屬性

CLSCompliantAttribute

範例

下列範例會將值的陣列 UInt16 轉換成 Boolean 值。

array<unsigned short>^ numbers = gcnew array<unsigned short> { UInt16::MinValue, 216, 21453, UInt16::MaxValue };
bool result;
   
for each (unsigned short number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-7:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       0        -->  False
//       216      -->  True
//       21,453   -->  True
//       65,535   -->  True

ushort[] numbers = { UInt16.MinValue, 216, 21453, UInt16.MaxValue };
bool result;

foreach (ushort number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-7:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       0        -->  False
//       216      -->  True
//       21,453   -->  True
//       65,535   -->  True

let numbers = 
    [| UInt16.MinValue; 216us; 21453us; UInt16.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-7:N0}  -->  {result}"
// The example displays the following output:
//       0        -->  False
//       216      -->  True
//       21,453   -->  True
//       65,535   -->  True

Dim numbers() As UShort = { UInt16.MinValue, 216, 21453, UInt16.MaxValue }
Dim result As Boolean

For Each number As UShort In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-7:N0}  -->  {1}", number, result)
Next
' The example displays the following output:
'       0        -->  False
'       216      -->  True
'       21,453   -->  True
'       65,535   -->  True

另請參閱

• UInt16

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::String ^ value);

public static bool ToBoolean (string value);

public static bool ToBoolean (string? value);

static member ToBoolean : string -> bool

Public Shared Function ToBoolean (value As String) As Boolean

參數

傳回

當 true 等於 value 時為 TrueString，否則，當 false 等於 value 或 FalseString 時，則為 null。

例外狀況

範例

下列範例會 Convert.ToBoolean(String) 使用 方法，將各種字串轉換成布爾值。

using namespace System;

void main()
{
   array<String^>^ values = gcnew array<String^> { nullptr, String::Empty,
                                                   "true", "TrueString",
                                                   "False", "    false    ",
                                                   "-1", "0" };
   for each (String^ value in values) {
      try
      {
         Console::WriteLine("Converted '{0}' to {1}.", value,  
                           Convert::ToBoolean(value));
      }
      catch (FormatException^ e)
      {
         Console::WriteLine("Unable to convert '{0}' to a Boolean.", value);
      }
   }
}
// The example displays the following output:
//       Converted '' to False.
//       Unable to convert '' to a Boolean.
//       Converted 'true' to True.
//       Unable to convert 'TrueString' to a Boolean.
//       Converted 'False' to False.
//       Converted '    false    ' to False.
//       Unable to convert '-1' to a Boolean.
//       Unable to convert '0' to a Boolean.

using System;

public class BooleanConversion
{
   public static void Main()
   {
      String[] values = { null, String.Empty, "true", "TrueString",
                          "False", "    false    ", "-1", "0" };
      foreach (var value in values) {
         try
         {
            Console.WriteLine("Converted '{0}' to {1}.", value,
                              Convert.ToBoolean(value));
         }
         catch (FormatException)
         {
            Console.WriteLine("Unable to convert '{0}' to a Boolean.", value);
         }
      }
   }
}
// The example displays the following output:
//       Converted '' to False.
//       Unable to convert '' to a Boolean.
//       Converted 'true' to True.
//       Unable to convert 'TrueString' to a Boolean.
//       Converted 'False' to False.
//       Converted '    false    ' to False.
//       Unable to convert '-1' to a Boolean.
//       Unable to convert '0' to a Boolean.

open System

let values =
    [| null; String.Empty; "true"; "TrueString"
       "False"; "    false    "; "-1"; "0" |]

for value in values do
    try
        printfn $"Converted '{value}' to {Convert.ToBoolean value}."
                        
    with :? FormatException ->
        printfn $"Unable to convert '{value}' to a Boolean."
// The example displays the following output:
//       Converted '' to False.
//       Unable to convert '' to a Boolean.
//       Converted 'true' to True.
//       Unable to convert 'TrueString' to a Boolean.
//       Converted 'False' to False.
//       Converted '    false    ' to False.
//       Unable to convert '-1' to a Boolean.
//       Unable to convert '0' to a Boolean.

Module BooleanConversion
   Public Sub Main()
      Dim values() As String = { Nothing, String.Empty, "true", 
                                 "TrueString", "False", "    false    ",
                                 "-1", "0" }
      For Each value In values                                 
         Try
            Console.WriteLine("Converted '{0}' to {1}.", value, _ 
                              Convert.ToBoolean(value))
         Catch e As FormatException
            Console.WriteLine("Unable to convert '{0}' to a Boolean.", value)
         End Try
      Next
   End Sub
End Module
' The example displays the following output to the console:
'       Converted '' to False.
'       Unable to convert '' to a Boolean.
'       Converted 'true' to True.
'       Unable to convert 'TrueString' to a Boolean.
'       Converted 'False' to False.
'       Converted '    false    ' to False.
'       Unable to convert '-1' to a Boolean.
'       Unable to convert '0' to a Boolean.

備註

若要成功進行轉換， value 參數必須等於 Boolean.TrueString、其值為 True的常數、 Boolean.FalseString值為 的常數 False，或必須是 null。 相較於 valueBoolean.TrueString 和 Boolean.FalseString，方法會忽略大小寫以及開頭和尾端空格符。

如果您不想在轉換失敗時處理例外狀況，您可以改為呼叫 Boolean.TryParse 方法。 它會傳回值 Boolean ，指出轉換成功或失敗。

另請參閱

• String

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(float value);

public static bool ToBoolean (float value);

static member ToBoolean : single -> bool

Public Shared Function ToBoolean (value As Single) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

範例

下列範例會將值的陣列 Single 轉換成 Boolean 值。

array<float>^ numbers = gcnew array<float> { Single::MinValue, (float) -193.0012, (float) 20e-15f, 0, 
                                             (float) 10551e-10, (float) 100.3398, Single::MaxValue };
bool result;
   
for each (float number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-15}  -->  {1}", number, result);
}
// The example displays the following output:
//       -3.402823E+38    -->  True
//       -193.0012        -->  True
//       2E-14            -->  True
//       0                -->  False
//       1.0551E-06       -->  True
//       100.3398         -->  True
//       3.402823E+38     -->  True

float[] numbers = { Single.MinValue, -193.0012f, 20e-15f, 0f,
                    10551e-10f, 100.3398f, Single.MaxValue };
bool result;

foreach (float number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-15}  -->  {1}", number, result);
}
// The example displays the following output:
//       -3.402823E+38    -->  True
//       -193.0012        -->  True
//       2E-14            -->  True
//       0                -->  False
//       1.0551E-06       -->  True
//       100.3398         -->  True
//       3.402823E+38     -->  True

let numbers = 
    [| Single.MinValue; -193.0012f; 20e-15f; 0f
       10551e-10f; 100.3398f; Single.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-15}  -->  {result}"
// The example displays the following output:
//       -3.402823E+38    -->  True
//       -193.0012        -->  True
//       2E-14            -->  True
//       0                -->  False
//       1.0551E-06       -->  True
//       100.3398         -->  True
//       3.402823E+38     -->  True

Dim numbers() As Single = { Single.MinValue, -193.0012, 20e-15, 0, _
                            10551e-10, 100.3398, Single.MaxValue }
Dim result As Boolean

For Each number As Single In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-15}  -->  {1}", number, result)
Next
' The example displays the following output:
'       -3.402823E+38    -->  True
'       -193.0012        -->  True
'       2E-14            -->  True
'       0                -->  False
'       1.0551E-06       -->  True
'       100.3398         -->  True
'       3.402823E+38     -->  True

另請參閱

• Single

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::Object ^ value);

public static bool ToBoolean (object value);

public static bool ToBoolean (object? value);

static member ToBoolean : obj -> bool

Public Shared Function ToBoolean (value As Object) As Boolean

參數

傳回

true 或 false，其會反映為 ToBoolean(IFormatProvider) 的基礎類型所叫用之 value 方法所傳回的值。 如果 value 是 null，則方法會傳回 false。

例外狀況

範例

下列範例會將物件值的陣列轉換成 Boolean 值。

array<Object^>^ objects = gcnew array<Object^> { 16.33, -24, 0, "12", "12.7", String::Empty, 
                                                "1String", "True", "false", nullptr, 
                                                gcnew System::Collections::ArrayList };

for each (Object^ obj in objects)
{
   Console::Write("{0,-40}  -->  ", 
                 obj == nullptr ? "null" :
                 String::Format("{0} ({1})", obj, obj->GetType()->Name));
   try {
      Console::WriteLine("{0}", Convert::ToBoolean((Object^) obj));
   }   
   catch (FormatException^) {
      Console::WriteLine("Bad Format");
   }   
   catch (InvalidCastException^) {
      Console::WriteLine("No Conversion");
   }   
}     
// The example displays the following output:
//       16.33 (Double)                            -->  True
//       -24 (Int32)                               -->  True
//       0 (Int32)                                 -->  False
//       12 (String)                               -->  Bad Format
//       12.7 (String)                             -->  Bad Format
//        (String)                                 -->  Bad Format
//       1String (String)                          -->  Bad Format
//       True (String)                             -->  True
//       false (String)                            -->  False
//       null                                      -->  False
//       System.Collections.ArrayList (ArrayList)  -->  No Conversion

object[] objects = { 16.33, -24, 0, "12", "12.7", String.Empty,
                     "1String", "True", "false", null,
                     new System.Collections.ArrayList() };

foreach (object obj in objects)
{
   Console.Write("{0,-40}  -->  ",
                 obj != null ?
                 String.Format("{0} ({1})", obj, obj.GetType().Name) :
                 "null");
   try {
      Console.WriteLine("{0}", Convert.ToBoolean(obj));
   }
   catch (FormatException) {
      Console.WriteLine("Bad Format");
   }
   catch (InvalidCastException) {
      Console.WriteLine("No Conversion");
   }
}
// The example displays the following output:
//       16.33 (Double)                            -->  True
//       -24 (Int32)                               -->  True
//       0 (Int32)                                 -->  False
//       12 (String)                               -->  Bad Format
//       12.7 (String)                             -->  Bad Format
//        (String)                                 -->  Bad Format
//       1String (String)                          -->  Bad Format
//       True (String)                             -->  True
//       false (String)                            -->  False
//       null                                      -->  False
//       System.Collections.ArrayList (ArrayList)  -->  No Conversion

let objects: obj[] =
    [| 16.33; -24; 0; "12"; "12.7"; String.Empty
       "1String"; "True"; "false"; null
       System.Collections.ArrayList() |]

for obj in objects do
    printf $"""{(if obj <> null then $"{obj} ({obj.GetType().Name})" else "null"),-40}  -->  """
    try
        Console.WriteLine("{0}", Convert.ToBoolean(obj))
    with
    | :? FormatException ->
        printfn "Bad Format"
    | :? InvalidCastException ->
        printfn "No Conversion"
// The example displays the following output:
//       16.33 (Double)                            -->  True
//       -24 (Int32)                               -->  True
//       0 (Int32)                                 -->  False
//       12 (String)                               -->  Bad Format
//       12.7 (String)                             -->  Bad Format
//        (String)                                 -->  Bad Format
//       1String (String)                          -->  Bad Format
//       True (String)                             -->  True
//       false (String)                            -->  False
//       null                                      -->  False
//       System.Collections.ArrayList (ArrayList)  -->  No Conversion

Dim objects() As Object = {16.33, -24, 0, "12", "12.7", String.Empty, _
                           "1String", "True", "false", Nothing, _
                           New System.Collections.ArrayList() }
For Each obj As Object In objects
   If obj IsNot Nothing Then
      Console.Write("{0,-40}  -->  ", _
                    String.Format("{0} ({1})", obj, obj.GetType().Name))
   Else
      Console.Write("{0,-40}  -->  ", "Nothing")   
   End If
   Try
      Console.WriteLine("{0}", Convert.ToBoolean(obj))
   Catch e As FormatException
      Console.WriteLine("Bad Format")
   Catch e As InvalidCastException
      Console.WriteLine("No Conversion")
   End Try   
Next     
' The example displays the following output:
'       16.33 (Double)                            -->  True
'       -24 (Int32)                               -->  True
'       0 (Int32)                                 -->  False
'       12 (String)                               -->  Bad Format
'       12.7 (String)                             -->  Bad Format
'        (String)                                 -->  Bad Format
'       1String (String)                          -->  Bad Format
'       True (String)                             -->  True
'       false (String)                            -->  False
'       Nothing                                   -->  False
'       System.Collections.ArrayList (ArrayList)  -->  No Conversion

另請參閱

• Object

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(DateTime value);

public static bool ToBoolean (DateTime value);

static member ToBoolean : DateTime -> bool

Public Shared Function ToBoolean (value As DateTime) As Boolean

參數

傳回

不支援此轉換。 沒有傳回值。

例外狀況

範例

下列範例示範嘗試將值轉換成 DateTime 布爾型別會 InvalidCastException擲回 。

public:
   void ConvertBoolean()
   {
      const int year = 1979;
      const int month = 7;
      const int day = 28;
      const int hour = 13;
      const int minute = 26;
      const int second = 15;
      const int millisecond = 53;
      DateTime dateTime( year, month, day, hour,
         minute, second, millisecond );
      bool boolVal;
      
      // System::InvalidCastException is always thrown.
      try
      {
         boolVal = System::Convert::ToBoolean( dateTime );
      }
      catch ( System::InvalidCastException^ ) 
      {
         System::Console::WriteLine( "Conversion from DateTime to Boolean "+
            "is not supported by the .NET Framework." );
      }
   }

public void ConvertBoolean() {
    const int year			= 1979;
    const int month			= 7;
    const int day			= 28;
    const int hour			= 13;
    const int minute		= 26;
    const int second		= 15;
    const int millisecond	= 53;

    DateTime dateTime = new DateTime(year, month, day, hour,
                                minute, second, millisecond);
    
    bool boolVal;

    // System.InvalidCastException is always thrown.
    try {
        boolVal = System.Convert.ToBoolean(dateTime);
    }
    catch (System.InvalidCastException) {
        System.Console.WriteLine("Conversion from DateTime to " +
            "Boolean is not supported by the .NET Framework.");
    }
}

let convertBoolean () =
    let year        = 1979
    let month       = 7
    let day         = 28
    let hour        = 13
    let minute      = 26
    let second      = 15
    let millisecond = 53

    let dateTime = DateTime(year, month, day, hour, minute, second, millisecond)

    // System.InvalidCastException is always thrown.
    try
        let boolVal = Convert.ToBoolean dateTime
        ()
    with :? InvalidCastException ->
        printfn "Conversion from DateTime to Boolean is not supported by the .NET Runtime."

Public Sub ConvertBoolean()
    Const year As Integer = 1979
    Const month As Integer = 7
    Const day As Integer = 28
    Const hour As Integer = 13
    Const minute As Integer = 26
    Const second As Integer = 15
    Const millisecond As Integer = 53

    Dim dateTime As New DateTime(year, month, day, hour, minute, _
                                 second, millisecond)

    Dim boolVal As Boolean

    ' System.InvalidCastException is always thrown.
    Try
        boolVal = System.Convert.ToBoolean(dateTime)
    Catch exception As System.InvalidCastException
        System.Console.WriteLine("Conversion from DateTime to " + _
                "Boolean is not supported by the .NET Framework.")
    End Try
End Sub

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(int value);

public static bool ToBoolean (int value);

static member ToBoolean : int -> bool

Public Shared Function ToBoolean (value As Integer) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

範例

下列範例會將值的陣列 Int32 轉換成 Boolean 值。

array<int>^ numbers = gcnew array<int> { Int32::MinValue, -201649, -68, 0, 612, 4038907, 
                                         Int32::MaxValue };
bool result;
   
for each (int number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-15:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       -2,147,483,648   -->  True
//       -201,649         -->  True
//       -68              -->  True
//       0                -->  False
//       612              -->  True
//       4,038,907        -->  True
//       2,147,483,647    -->  True

int[] numbers = { Int32.MinValue, -201649, -68, 0, 612, 4038907,
                  Int32.MaxValue };
bool result;

foreach (int number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-15:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       -2,147,483,648   -->  True
//       -201,649         -->  True
//       -68              -->  True
//       0                -->  False
//       612              -->  True
//       4,038,907        -->  True
//       2,147,483,647    -->  True

let numbers = 
    [| Int32.MinValue; -201649; -68; 0
       612; 4038907; Int32.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-15:N0}  -->  {result}"
// The example displays the following output:
//       -2,147,483,648   -->  True
//       -201,649         -->  True
//       -68              -->  True
//       0                -->  False
//       612              -->  True
//       4,038,907        -->  True
//       2,147,483,647    -->  True

Dim numbers() As Integer = { Int32.MinValue, -201649, -68, 0, 612, _
                             4038907, Int32.MaxValue }
Dim result As Boolean

For Each number As Integer In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-15:N0}  -->  {1}", number, result)
Next
' The example displays the following output:
'       -2,147,483,648   -->  True
'       -201,649         -->  True
'       -68              -->  True
'       0                -->  False
'       612              -->  True
'       4,038,907        -->  True
'       2,147,483,647    -->  True

另請參閱

• Int32

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(short value);

public static bool ToBoolean (short value);

static member ToBoolean : int16 -> bool

Public Shared Function ToBoolean (value As Short) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

範例

下列範例會將值的陣列 Int16 轉換成 Boolean 值。

array<Int16>^ numbers = gcnew array<Int16> { Int16::MinValue, -10000, -154, 0, 216, 21453, 
                                       Int16::MaxValue };
bool result;
   
for each (Int16 number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-7:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       -32,768  -->  True
//       -10,000  -->  True
//       -154     -->  True
//       0        -->  False
//       216      -->  True
//       21,453   -->  True
//       32,767   -->  True

short[] numbers = { Int16.MinValue, -10000, -154, 0, 216, 21453,
                    Int16.MaxValue };
bool result;

foreach (short number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-7:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       -32,768  -->  True
//       -10,000  -->  True
//       -154     -->  True
//       0        -->  False
//       216      -->  True
//       21,453   -->  True
//       32,767   -->  True

let numbers = 
    [| Int16.MinValue; -10000s; -154s; 0s
       216s; 21453s; Int16.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-7:N0}  -->  {result}"
// The example displays the following output:
//       -32,768  -->  True
//       -10,000  -->  True
//       -154     -->  True
//       0        -->  False
//       216      -->  True
//       21,453   -->  True
//       32,767   -->  True

Dim numbers() As Short = { Int16.MinValue, -10000, -154, 0, 216, _
                           21453, Int16.MaxValue }
Dim result As Boolean

For Each number As Short In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-7:N0}  -->  {1}", number, result)
Next
' The example displays the following output:
'       -32,768  -->  True
'       -10,000  -->  True
'       -154     -->  True
'       0        -->  False
'       216      -->  True
'       21,453   -->  True
'       32,767   -->  True

另請參閱

• Int16

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(double value);

public static bool ToBoolean (double value);

static member ToBoolean : double -> bool

Public Shared Function ToBoolean (value As Double) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

範例

下列範例會將布爾值轉換成 ， Double 並將 Double 轉換為布爾值。

public:
   void ConvertDoubleBool( double doubleVal )
   {
      bool boolVal;
      
      // Double to bool conversion cannot overflow.
      boolVal = System::Convert::ToBoolean( doubleVal );
      System::Console::WriteLine( " {0} as a Boolean is: {1}.",
         doubleVal, boolVal );
      
      // bool to double conversion cannot overflow.
      doubleVal = System::Convert::ToDouble( boolVal );
      System::Console::WriteLine( " {0} as a double is: {1}.",
         boolVal, doubleVal );
   }

public void ConvertDoubleBool(double doubleVal) {
    bool	boolVal;
    // Double to bool conversion cannot overflow.
    boolVal = System.Convert.ToBoolean(doubleVal);
    System.Console.WriteLine("{0} as a Boolean is: {1}.",
        doubleVal, boolVal);

    // bool to double conversion cannot overflow.
    doubleVal = System.Convert.ToDouble(boolVal);
    System.Console.WriteLine("{0} as a double is: {1}.",
        boolVal, doubleVal);
}

let convertDoubleBool (doubleVal: float) =
    // Double to bool conversion cannot overflow.
    let boolVal = Convert.ToBoolean doubleVal
    printfn $"{doubleVal} as a Boolean is: {boolVal}."

    // bool to double conversion cannot overflow.
    let doubleVal = Convert.ToDouble boolVal
    printfn $"{boolVal} as a double is: {doubleVal}."

Public Sub ConvertDoubleBool(ByVal doubleVal As Double)
    Dim boolVal As Boolean

    'Double to Boolean conversion cannot overflow.
    boolVal = System.Convert.ToBoolean(doubleVal)
    System.Console.WriteLine("{0} as a Boolean is: {1}.", _
                              doubleVal, boolVal)

    'Boolean to Double conversion cannot overflow.
    doubleVal = System.Convert.ToDouble(boolVal)
    System.Console.WriteLine("{0} as a Double is: {1}.", _
                              boolVal, doubleVal)
End Sub

另請參閱

• Double

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::Decimal value);

public static bool ToBoolean (decimal value);

static member ToBoolean : decimal -> bool

Public Shared Function ToBoolean (value As Decimal) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

範例

下列範例會將值的陣列 Decimal 轉換成 Boolean 值。

array<Decimal>^ numbers = gcnew array<Decimal> { Decimal::MinValue, (Decimal) -12034.87, 
                                                 (Decimal) -100, (Decimal) 0, (Decimal) 300, 
                                                 (Decimal) 6790823.45, Decimal::MaxValue };
bool result;

for each (Decimal number in numbers)
{
   result = Convert::ToBoolean(number); 
   Console::WriteLine("{0,-30}  -->  {1}", number, result);
}
// The example displays the following output:
//       -79228162514264337593543950335  -->  True
//       -12034.87                       -->  True
//       -100                            -->  True
//       0                               -->  False
//       300                             -->  True
//       6790823.45                      -->  True
//       79228162514264337593543950335   -->  True

decimal[] numbers = { Decimal.MinValue, -12034.87m, -100m, 0m,
                             300m, 6790823.45m, Decimal.MaxValue };
bool result;

foreach (decimal number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-30}  -->  {1}", number, result);
}
// The example displays the following output:
//       -79228162514264337593543950335  -->  True
//       -12034.87                       -->  True
//       -100                            -->  True
//       0                               -->  False
//       300                             -->  True
//       6790823.45                      -->  True
//       79228162514264337593543950335   -->  True

let numbers = 
    [| Decimal.MinValue; -12034.87m; -100m; 0m
       300m; 6790823.45m; Decimal.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-30}  -->  {result}"
// The example displays the following output:
//       -79228162514264337593543950335  -->  True
//       -12034.87                       -->  True
//       -100                            -->  True
//       0                               -->  False
//       300                             -->  True
//       6790823.45                      -->  True
//       79228162514264337593543950335   -->  True

Dim numbers() As Decimal = { Decimal.MinValue, -12034.87d, -100d, _
                             0d, 300d, 6790823.45d, Decimal.MaxValue }
Dim result As Boolean

For Each number As Decimal In numbers
   result = Convert.ToBoolean(number) 
   Console.WriteLine("{0,-30}  -->  {1}", number, result)
Next
' The example displays the following output:
'       -79228162514264337593543950335  -->  True
'       -12034.87                       -->  True
'       -100                            -->  True
'       0                               -->  False
'       300                             -->  True
'       6790823.45                      -->  True
'       79228162514264337593543950335   -->  True

另請參閱

• Decimal

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(char value);

public static bool ToBoolean (char value);

static member ToBoolean : char -> bool

Public Shared Function ToBoolean (value As Char) As Boolean

參數

傳回

不支援此轉換。 沒有傳回值。

例外狀況

另請參閱

• Char

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(System::Byte value);

public static bool ToBoolean (byte value);

static member ToBoolean : byte -> bool

Public Shared Function ToBoolean (value As Byte) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

範例

下列範例會將值的陣列 Byte 轉換成 Boolean 值。

array<Byte>^ bytes = gcnew array<Byte> { Byte::MinValue, 100, 200, Byte::MaxValue };
bool result;
   
for each (Byte byteValue in bytes)
{
   result = Convert::ToBoolean(byteValue); 
   Console::WriteLine("{0,-5}  -->  {1}", byteValue, result);
}           
// The example displays the following output:
//       0      -->  False
//       100    -->  True
//       200    -->  True
//       255    -->  True

byte[] bytes = { Byte.MinValue, 100, 200, Byte.MaxValue };
bool result;

foreach (byte byteValue in bytes)
{
   result = Convert.ToBoolean(byteValue);
   Console.WriteLine("{0,-5}  -->  {1}", byteValue, result);
}
// The example displays the following output:
//       0      -->  False
//       100    -->  True
//       200    -->  True
//       255    -->  True

let bytes = [| Byte.MinValue; 100uy; 200uy; Byte.MaxValue |]

for byteValue in bytes do
    let result = Convert.ToBoolean byteValue
    printfn $"{byteValue,-5}  -->  {result}"
// The example displays the following output:
//       0      -->  False
//       100    -->  True
//       200    -->  True
//       255    -->  True

Dim bytes() As Byte = { Byte.MinValue, 100, 200, Byte.MaxValue }
Dim result As Boolean

For Each byteValue As Byte In bytes
   result = Convert.ToBoolean(byteValue) 
   Console.WriteLine("{0,-5}  -->  {1}", byteValue, result)
Next           
' The example displays the following output:
'       0      -->  False
'       100    -->  True
'       200    -->  True
'       255    -->  True

另請參閱

• Byte

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(bool value);

public static bool ToBoolean (bool value);

static member ToBoolean : bool -> bool

Public Shared Function ToBoolean (value As Boolean) As Boolean

參數

傳回

value 會原封不動地傳回。

另請參閱

• Boolean

來源:

Convert.cs

來源:

Convert.cs

來源:

Convert.cs

public:
 static bool ToBoolean(long value);

public static bool ToBoolean (long value);

static member ToBoolean : int64 -> bool

Public Shared Function ToBoolean (value As Long) As Boolean

參數

傳回

如果 true 不是零，則為 value，否則為 false。

範例

下列範例會將值的陣列 Int64 轉換成 Boolean 值。

array<Int64>^ numbers = gcnew array<Int64> { Int64::MinValue, -2016493, -689, 0, 6121, 
                                           403890774, Int64::MaxValue };
bool result;
   
for each (Int64 number in numbers)
{
   result = Convert::ToBoolean(number);                                 
   Console::WriteLine("{0,-26:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       -9,223,372,036,854,775,808  -->  True
//       -2,016,493                  -->  True
//       -689                        -->  True
//       0                           -->  False
//       6,121                       -->  True
//       403,890,774                 -->  True
//       9,223,372,036,854,775,807   -->  True

long[] numbers = { Int64.MinValue, -2016493, -689, 0, 6121,
                   403890774, Int64.MaxValue };
bool result;

foreach (long number in numbers)
{
   result = Convert.ToBoolean(number);
   Console.WriteLine("{0,-26:N0}  -->  {1}", number, result);
}
// The example displays the following output:
//       -9,223,372,036,854,775,808  -->  True
//       -2,016,493                  -->  True
//       -689                        -->  True
//       0                           -->  False
//       6,121                       -->  True
//       403,890,774                 -->  True
//       9,223,372,036,854,775,807   -->  True

let numbers =
    [| Int64.MinValue; -2016493; -689
       0; 6121; 403890774; Int64.MaxValue |]

for number in numbers do
    let result = Convert.ToBoolean number
    printfn $"{number,-26:N0}  -->  {result}"
// The example displays the following output:
//       -9,223,372,036,854,775,808  -->  True
//       -2,016,493                  -->  True
//       -689                        -->  True
//       0                           -->  False
//       6,121                       -->  True
//       403,890,774                 -->  True
//       9,223,372,036,854,775,807   -->  True

Dim numbers() As Long = { Int64.MinValue, -2016493, -689, 0, 6121, _
                          403890774, Int64.MaxValue }
Dim result As Boolean

For Each number As Long In numbers
   result = Convert.ToBoolean(number)                                 
   Console.WriteLine("{0,-26:N0}  -->  {1}", number, result)
Next
' The example displays the following output:
'       -9,223,372,036,854,775,808  -->  True
'       -2,016,493                  -->  True
'       -689                        -->  True
'       0                           -->  False
'       6,121                       -->  True
'       403,890,774                 -->  True
'       9,223,372,036,854,775,807   -->  True

另請參閱

• Int64