How to send a windows message from C# to C++ (MFC)?

Hello mates,

I'm trying to send a windowsmessage from an app in C# (Compact Frame) to another one in C++ (MFC), both of them in a PDA.

In the receiver app (MFC) I realize that I receive the message but I can't read the string message, it shows a little square.

This is the code of the Sender (C#)

OpenNETCF.Win32.Win32Window.SendMessage(hwndVal, typeMsgVal, intValue, stringMessage);

And this is the code of the receiver (C++)

CString myStr = (CString) lParam;
    AfxMessageBox(myStr);

Thanks a lot in advance!