Json helper class in C++

Question

Json helper class in C++

Noah Aas 725

Hello,

I need to send data from C++ to C#.

I would like to use the Marshal interface.

How can I serialise a data structure in C++?

What is the best way to deserialise it in C#?

Is there a json helper class in C++?

class MachineData
{
   public:
      int X;
      double Speed;
      CString MachineId;
      CStringArray ArrayData;
      CIntArray ArrayDataIndex;

RLWA32 47,776 Reputation points

2025-03-15T08:19:08.9666667+00:00

I need to send data from C++ to C#.

Please be more specific about what you want to accomplish. Do you want to make data from unmanaged C++ code accessible to managed C# code within the same process? Is this data to be passed as a parameter to a method in a C# assembly? Passed between different processes?

Can you add CLR support to your C++ application?

With respect to the "MachineData" don't forget that C# doesn't know anything about C++ classes.

And from the .Net Framework docs - https://learn.microsoft.com/en-us/dotnet/framework/interop/interop-marshalling
Noah Aas 725 Reputation points

2025-03-15T13:22:14.45+00:00
Thank you for the quick reply.

The C++ receives data from a PLC, no changes possible. I need to send this data to a C# application.

Marshalling Since a string exchange worked, it would be easiest if I could serialise the data in C++ and deserialise it in C+. The question is how can I achieve this?

C# ---- CopyData(Marshalling) --- C++ -----PLC

CopyData(Marshalling) -- is only a string, so the best is JSON. CLI is not possible I need unmanaged code.
If serialisation is not possible, I have to find a dirty solution, like
X,Speed, MachineID, [, ArrayData, ] .... to send data from the C++ app to the C# app. I have to define my own structure. It would be better if I could use something that has been checked.

Thanks for any further tips in advance.
Darran Rowe 1,516 Reputation points

2025-03-15T20:31:00.16+00:00

C++ doesn't have reflection, so there is no way to do this automatically. If the class only contains simple types then it should be easy to do this manually. Windows also comes with a JSON library as part of the WinRT API. This is fully usable in desktop C++ applications, and it can be fully native.
Noah Aas 725 Reputation points

2025-03-16T13:57:11.35+00:00

Windows also comes with a JSON library as part of the WinRT API. This is fully usable in desktop C++ applications, and it can be fully native.

OK, Do you have an example? What do I have to integrate?

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RLWA32 47,776 Reputation points

2025-03-15T08:19:08.9666667+00:00

I need to send data from C++ to C#.

Please be more specific about what you want to accomplish. Do you want to make data from unmanaged C++ code accessible to managed C# code within the same process? Is this data to be passed as a parameter to a method in a C# assembly? Passed between different processes?

Can you add CLR support to your C++ application?

With respect to the "MachineData" don't forget that C# doesn't know anything about C++ classes.

And from the .Net Framework docs - https://learn.microsoft.com/en-us/dotnet/framework/interop/interop-marshalling
Noah Aas 725 Reputation points

2025-03-15T13:22:14.45+00:00

Thank you for the quick reply.

The C++ receives data from a PLC, no changes possible. I need to send this data to a C# application.

Marshalling Since a string exchange worked, it would be easiest if I could serialise the data in C++ and deserialise it in C+. The question is how can I achieve this?

C# ---- CopyData(Marshalling) --- C++ -----PLC

CopyData(Marshalling) -- is only a string, so the best is JSON. CLI is not possible I need unmanaged code.
If serialisation is not possible, I have to find a dirty solution, like
X,Speed, MachineID, [, ArrayData, ] .... to send data from the C++ app to the C# app. I have to define my own structure. It would be better if I could use something that has been checked.

Thanks for any further tips in advance.
Darran Rowe 1,516 Reputation points

2025-03-15T20:31:00.16+00:00

C++ doesn't have reflection, so there is no way to do this automatically. If the class only contains simple types then it should be easy to do this manually. Windows also comes with a JSON library as part of the WinRT API. This is fully usable in desktop C++ applications, and it can be fully native.
Noah Aas 725 Reputation points

2025-03-16T13:57:11.35+00:00

Windows also comes with a JSON library as part of the WinRT API. This is fully usable in desktop C++ applications, and it can be fully native.

OK, Do you have an example? What do I have to integrate?

Answer 1

Minxin Yu 13,326 Microsoft External Staff

Hi,
To use WinRT API, make sure templates is installed.
The template projects have already configured the settings required for C++/WinRt.
User's image

For example:
User's image

#include"pch.h"
#include <winrt/Windows.Foundation.h>
#include <winrt/Windows.Data.Json.h>
#include <winrt/Windows.Foundation.Collections.h>
#include <iostream>

using namespace winrt;

using namespace Windows::Data::Json;

int main () {

    init_apartment ();

    JsonObject obj;
    obj.Insert (L"message", JsonValue::CreateStringValue (L"Hello from C++/WinRT!"));
    obj.Insert (L"year", JsonValue::CreateNumberValue (2025)); //parameter: double input

    JsonArray arr;

    arr.Append (JsonValue::CreateStringValue (L"one"));
    arr.Append (JsonValue::CreateStringValue (L"two"));
    arr.Append (JsonValue::CreateStringValue (L"three"));
    obj.Insert (L"list", arr);

    hstring jsonStr = obj.Stringify (); //jsonStr = L"{\"message\":\"Hello from C++/WinRT!\",\"year\":2025,\"list\":[\"one\",\"two\",\"three\"]}"

    //string data

    std::wcout << L"Serialized JSON: " << jsonStr.c_str () << std::endl;
    std::string tempStr(jsonStr.begin (), jsonStr.end ());
    std::cout << "Serialized JSON: " << tempStr.c_str () << std::endl;

    return 0;

}

enter image description here

Best regards,

Minxin Yu

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Noah Aas 725 Reputation points

2025-03-17T14:36:31.7633333+00:00

That looks good. Many thanks for your help.

I'll check it out as soon as possible. I can simply create a JSON structure here. Using my class, I have to convert this into JSON form.

MyObject.Serialise does not work like in C#? I see that correctly. I could create the JSON format as described by you, send it to C# and deserialise it there. I think this is a good way, how do you see my plan? Is it good or bad?

It should also work with a dialogue-based application in MFC. Do you still see problems, or hurdles?
Minxin Yu 13,326 Reputation points Microsoft External Staff

2025-03-18T01:25:13.0333333+00:00

It should work fine in MFC. If you are looking for an official library, JsonObject is a good choice.
Noah Aas 725 Reputation points

2025-03-18T10:11:40.4766667+00:00
Works nearly.

How I can convert a CString to hstring?

How I can convert hstring to CString?

Thanks for your help. I have CString in my class.

hondaman-3591 81

@Noah Aas

    CStringW strW = jsonStr.c_str ();
    CStringA strA = tempStr.c_str ();
    hstring hstrW = strW.GetString ();    
    hstring hstr = CA2W (strA).m_psz;
        
    std::wcout << L"Serialized JSON: " << hstrW.c_str () << std::endl;
    std::wcout << L"Serialized JSON: " << hstr.c_str () << std::endl;

Noah Aas 725 Reputation points

2025-03-18T15:30:14.69+00:00

And please one sample with CString MFC.

Thanks in advance.

Minxin Yu 13,326 Microsoft External Staff

There is CString sample above. CString maps to either CStringA or CStringW depending on whether the UNICODE macro is defined.

#ifdef UNICODE // UNICODE
    CString strW = jsonStr.c_str ();
    hstring hstr = strW.GetString ();
    std::wcout << L"Serialized JSON: " << hstr.c_str () << std::endl;
#else //ANSI
    std::string tempStr (jsonStr.begin (), jsonStr.end ());
    CString strA = tempStr.c_str ();    
    hstring hstr = CA2W (strA).m_psz;
    std::wcout << L"Serialized JSON: " << hstr.c_str () << std::endl;
#endif

Noah Aas 725 Reputation points

2025-03-19T12:40:59.6466667+00:00

Thank you for the sample.

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Json helper class in C++

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