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        #region SendReceiveMessage

        [DllImport("user32.dll")]
        public static extern IntPtr FindWindow(string strClassName, string strWindowName);

        [DllImport("user32.dll")]
        public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr
        lParam);

        public const int WM_APP = 0x8000;
        public const int WM_MYMSG =WM_APP + 0x100;
        

        void SendMessageToUnmanaged()
        {
            IntPtr hWnd = FindWindow(null, "Fenstername");

            string s = "Somestring";

            IntPtr sNative = Marshal.StringToHGlobalAuto(s);
            IntPtr result = SendMessage(hWnd, WM_MYMSG, (IntPtr)1234, sNative);
            Marshal.FreeHGlobal(sNative);
          

            /*
            IntPtr ptr = Marshal.StringToHGlobalAnsi(Environment.CommandLine);
            IntPtr result = SendMessage(hWnd, WM_MYMSG, (IntPtr)1234, ptr);
             */


        }

        #endregion					

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BEGIN_MESSAGE_MAP(CIProgDlg, CDialog)
  ON_WM_PAINT()
  ON_WM_QUERYDRAGICON()
  //}}AFX_MSG_MAP
  ON_BN_CLICKED(IDC_BUTTON2, &CIProgDlg::OnBnClickedButton2)

  // Eigene Message
  ON_MESSAGE ( WM_MYMSG, OnMyMsg )
END_MESSAGE_MAP()


// Eigene Message
LRESULT CIProgDlg::OnMyMsg(WPARAM wParam, LPARAM lParam)
{
  int wP = wParam;
  char* lP = (char*)lParam;

  return MessageBox(L"Hello",L"Top",MB_OK);
}