Re: communication between C# dll and C++ dll ???

<njoycod...@gmail.com> ha scritto nel messaggio
news:00b9e7ea-db4f-41bf-98ae-ea0d142a5099@v26g2000prm.googlegroups.com...=


Suppose that you have a C# class that has a read-write 'Text' property
which is a String (C# .NET String).
This class is called 'CSharpClass' and is in the namespace TestCSharpLib=

* CSharpClass:
- properties:
   + Text (String) (read/write)
- methods:
   + SayHello

You can use the new marshal library in VS2008 to help you marshal string=

between C++ and C#.

Suppose you have an MFC application (.exe) and you want to marshal the
string from C++ (CStringW / const wchar_t *) to C#, and back.

First you must enable CLR support in the MFC .exe.
You can do that selecting the properties menu of your MFC project (right=

click on project item in Solution Explorer, and select 'Properties' in t=

popup menu).

Then select 'Configuration Properties'.
Then, in the item 'Common Language Runtime support: ', select the value:=

'Common Language Runtime support (/clr)'

Then you should include the following lines after the normal #include's
lines in the .cpp source file where you are going to call the C# class.
The purpose of these lines is to use the marshal library of VS2008:

<code>
// Use the marshal library in VS2008
#include <msclr/marshal.h>
using namespace msclr::interop;
</code>

At this point, you can use the marshal_as<> template.

I posted a sample code from a project of mine, that does both directions=

marshaling: C++ -> C# and back C# --> C++.
The code is commented, so you can read the comments for each step:

<code>

//
// TEST of string marshaling between C# and C++
//
void CMfcCallsCSharpDlg::OnBnClickedBtnCallCs()
{
   // Create an instance of the C# class
   // on the managed heap (using gcnew)
   TestCSharpLib1::CSharpClass ^ csharpClass = gcnew
TestCSharpLib1::CSharpClass();

   // Read user's text from edit control
   CStringW strText;
   m_txtInput.GetWindowText( strText );

   // Prepare marshal context for marshaling string between C# and C=

   marshal_context ^ marshalCtx = gcnew marshal_context();

   //
   // Marshal string from C++ (CStringW - const wchar_t *)
   // to C# (System::String ^)
   //
   System::String ^ s = marshalCtx->marshal_as< System::String ^ >=

static_cast< PCWSTR >( strText ) );

   // Set string property into C# object
   csharpClass->Text = s;

   // Invoke test method of C# object
   csharpClass->SayHello();

   //
   // Inverse marshaling, from C# to C++
   //

   // Convert from C# string back to C++ string
   CStringW strFromCS;
   strFromCS = marshalCtx->marshal_as< PCWSTR >( csharpClass->Text=

   // Show the string from C#
   CStringW strMsg = L"String from C# : ";
   strMsg += strFromCS;
   AfxMessageBox( strMsg );

   // Cleanup marshal context
   delete marshalCtx;
}

</code>

Another option to communicate between C# and C++ is to use COM, but I do=

prefer the C++/CLI extensions of VS2008 - I think that it is simpler.

However, if your C++ MFC project is built using Visual C++ 6, you must u=

COM, because there is no C++/CLI extension in Visual C++ 6.
(C++/CLI extensions are one of the top reasons to move to VS2008, IMHO.)=

HTH,
Giovanni- Hide quoted text -