SortDescriptor Class

Article
01/27/2012

[WCF RIA Services Version 1 Service Pack 2 is compatible with either .NET framework 4 or .NET Framework 4.5, and with either Silverlight 4 or Silverlight 5.]

Describes a sorting criterion.

Inheritance Hierarchy

System.Object
System.Windows.DependencyObject
System.Windows.Controls.SortDescriptor

Namespace: System.Windows.Controls
Assembly: System.Windows.Controls.DomainServices (in System.Windows.Controls.DomainServices.dll)

Syntax

'Declaration
Public Class SortDescriptor _
    Inherits DependencyObject

'Usage
Dim instance As SortDescriptor

public class SortDescriptor : DependencyObject

public ref class SortDescriptor : public DependencyObject

type SortDescriptor =  
    class
        inherit DependencyObject
    end

public class SortDescriptor extends DependencyObject

The SortDescriptor type exposes the following members.

Constructors

	Name	Description
	SortDescriptor()	Initializes a new instance of the SortDescriptor class with default property values.
	SortDescriptor(String, ListSortDirection)	Initializes a new instance of the SortDescriptor class with the specified property to use for sorting, and the sort direction.

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Properties

	Name	Description
	Direction	Gets or sets the sort direction.
	Dispatcher	(Inherited from DependencyObject.)
	PropertyPath	Gets or sets the public property used to sort.

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Methods

	Name	Description
	CheckAccess	(Inherited from DependencyObject.)
	ClearValue	(Inherited from DependencyObject.)
	Equals	(Inherited from Object.)
	Finalize	(Inherited from Object.)
	GetAnimationBaseValue	(Inherited from DependencyObject.)
	GetHashCode	(Inherited from Object.)
	GetType	(Inherited from Object.)
	GetValue	(Inherited from DependencyObject.)
	MemberwiseClone	(Inherited from Object.)
	ReadLocalValue	(Inherited from DependencyObject.)
	SetValue	(Inherited from DependencyObject.)
	ToString	(Inherited from Object.)

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Fields

	Name	Description
	DirectionProperty	Identifies the Direction dependency property.
	PropertyPathProperty	Identifies the PropertyPath dependency property.

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Remarks

The DomainDataSource class provides the SortDescriptors collection to facilitate sorting data. In the SortDescriptors collection, you add SortDescriptor instances that describe the values to use for sorting the collection. You can add as many SortDescriptor instances as you want to provide layers of sorting. You can specify if the data is sorted in ascending or descending order.

If you use SortDescriptor programmatically, verify that the CanLoad property returns true. Attempting to sort when CanLoad returns false, causes the DomainDataSource to throw an invalid operation exception. Sorting initiates a load operation, and load operations are not permitted when CanLoad is false.

Examples

The following example shows how to add a sort descriptor to the DomainDataSource. The data retrieved from the query is sorted by values in the StandardCost property.

<Grid x:Name="LayoutRoot" Background="White">  
    <riaControls:DomainDataSource x:Name="source" QueryName="GetProducts" AutoLoad="true">
        <riaControls:DomainDataSource.DomainContext>
            <domain:ProductDomainContext />
        </riaControls:DomainDataSource.DomainContext>   
        <riaControls:DomainDataSource.SortDescriptors>
            <riaData:SortDescriptor PropertyPath="StandardCost" Direction="Ascending" />
            <riaData:SortDescriptor PropertyPath="ProductID" Direction="Ascending" />
        </riaControls:DomainDataSource.SortDescriptors>
    </riaControls:DomainDataSource>
    <data:DataGrid ItemsSource="{Binding Data, ElementName=source}" />
</Grid>

When you implement paging and sorting together, include at least one SortDescriptor with its PropertyPath attribute assigned to a property that contains unique values, such as a primary key. Or add an OrderBy clause based on a property that contains unique values to the query in the DomainDataSource. If you only sort the data on a property that does not contain unique values, the return values could contain inconsistent or missing data across pages.

For example, consider the values in the following table. Note that the ID values are unique, but the Country values are not unique.

ID	Country
1	UK
2	UK
3	US
4	UK
5	US
6	IT
7	UK
8	UK
9	US
10	SP

If you want to implement paging for these values, sorted by Country, you could use the following markup:

<Grid x:Name="LayoutRoot">
    <ScrollViewer x:Name="PageScrollViewer" Style="{StaticResource PageScrollViewerStyle}">
        <StackPanel x:Name="ContentStackPanel">
            <TextBlock x:Name="HeaderText" Style="{StaticResource HeaderTextStyle}" 
                               Text="Home"/>
            <TextBlock x:Name="ContentText" Style="{StaticResource ContentTextStyle}" 
                               Text="Home page content"/>
            <riaControls:DomainDataSource Name="domainDataSource1" QueryName="GetCountriesQuery" PageSize="4">
                <riaControls:DomainDataSource.DomainContext>
                    <ds:TestDomainContext></ds:TestDomainContext>
                </riaControls:DomainDataSource.DomainContext>
                <riaControls:DomainDataSource.SortDescriptors>
                    <riaControls:SortDescriptor PropertyPath="Country" Direction="Ascending"></riaControls:SortDescriptor>
                    <riaControls:SortDescriptor PropertyPath="ID"></riaControls:SortDescriptor>
                </riaControls:DomainDataSource.SortDescriptors>
            </riaControls:DomainDataSource>
            <my:DataGrid ItemsSource="{Binding Data, ElementName=domainDataSource1}" />
            <my:DataPager PageSize="4" Source="{Binding Data, ElementName=domainDataSource1}" />
        </StackPanel>
    </ScrollViewer>
</Grid>

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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