m_pMainWnd is the member of which class in MFC class hierarchy?

m_pMainWnd is the public member of CWinThread. This is mainly used when dealing with a UI thread and there is a top level main window. Every MFC application should have a main application thread. This main thread is implemented by CWinApp which is derived from CWinThread. Every application should create a main overlapped window and assign this main window pointer to m_pMainWnd. m_pMainWnd is the member to pass main window pointer from application to MFC framework which is used in CWinApp or CWinThread.

Source Code

#include <windows.h>

#include <afxwin.h>

class CMyWnd : public CFrameWnd
{
  public:
    CMyWnd()
    {
      Create(NULL, _T("My MFC Window"));
    }
    afx_msg void CMyWnd::OnClose();

    DECLARE_MESSAGE_MAP()
};
BEGIN_MESSAGE_MAP(CMyWnd, CFrameWnd)
ON_WM_CLOSE()
END_MESSAGE_MAP()

afx_msg void CMyWnd::OnClose()
{

  PostQuitMessage(0);

}
 
class CMyApp : public  CWinApp 
{

  public:
     virtual BOOL InitInstance()
    {
      m_pMainWnd = new CMyWnd();
      m_pMainWnd->ShowWindow(SW_SHOW);
      m_pMainWnd->UpdateWindow();
      return TRUE;
    }
 };
CMyApp app;

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