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Ken Beauchesne - 26 Sep 2005 19:09 GMT

I have a stand alone c++ program that uses SendMessage to communicate with
a stand alone C# program.

The c++ program looks like this

hWind has previously been determined;

wchar_t wts[] = L"123456";

::MessageBox(NULL,wts,L"",MB_OK); // just to display it gets set

SendMessage(hWind,WM_GET_ENG_UNITS_MESSAGE,0,(LPARAM)(&wts)); // send it
to the C# program

::MessageBox(NULL,wts,L"",MB_OK); // contents after the C# program

-----------------------------------------

The C# side catches the message and :

string EuS = Marshal.PtrToStringUni(msg.LParam);

EuS now reads correctly 123456

here lies my problem how can I minuplate the string on the c++ side from
the C# side by using the msg.LParam.

TIA
Ken

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Robert Jordan - 26 Sep 2005 20:28 GMT

Hi Ken,

> I have a stand alone c++ program that uses SendMessage to communicate with
> a stand alone C# program.
[quoted text clipped - 20 lines]
> here lies my problem how can I minuplate the string on the c++ side from
> the C# side by using the msg.LParam.

You cannot do that. Even with 2 C++ apps. Your WM_GET_ENG_UNITS_MESSAGE
message is probably identical with a Window message that takes
a LPTSTR as a LPARAM parameter. That's why the pointer got mapped
at all.

If you want to safely exchange data between the apps, you have
to use WM_COPYDATA:

http://www.vbaccelerator.com/home/NET/Code/Libraries/Windows_Messages/Simple_Int
erprocess_Communication/article.asp
http://www.codeproject.com/csharp/wm_copydata_use.asp

Rob

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