I am trying to send a user defined message to a secondary thread in my dialog based MFC application. My secondary thread is a derivative of the CWinThread class and I am launching it using:


From my main GUI thread, I would like to send a message to this secondary thread, I am using:


My problem however is that when I do this, I get an error code 1400: invalid window handle.

How would I go about getting a valid handle to my thread class?

Is there an easier / better way to accomplish this?

The ultimate reason I am doing this is to send a CString to my second thread when a button is clicked in my main GUI thread.

Thanks in advance for the help, I am very new to MFC / VC++
-Mike Visconti

A (despite its name) "user interface thread" does not have a window associated with it by default. If you want to use any function that requires a window handle (HWND) you need to create a window (can be invisible) first.

I much prefer to use PostThreadMessage, it takes a thread id as destination. The m_nThreadID member of the CWinThread class serves well for this purpose. Use ON_THREAD_MESSAGE macro in your message map to catch the messages.

e.g