ウィンドウハンドルを取得し、クリックボタンのメッセージを送信

    [DllImport("User32.dll ")]
        public static extern System.IntPtr FindWindowEx(System.IntPtr parent, System.IntPtr childe, string strclass, string strname);
        [DllImport("user32.dll", EntryPoint = "SendMessageA")]
        private static extern int SendMessage(IntPtr hwnd, int wMsg, IntPtr wParam, IntPtr lParam);

  static void Main(string[] args)

{
          IntPtr p = System.IntPtr.Zero;
            p = FindWindowEx(System.IntPtr.Zero, System.IntPtr.Zero, "MsiDialogCloseClass", "eFax");
            Debug.WriteLine("Try count:" + count + ":and the handle value of p is==>" + p);
            if (p != IntPtr.Zero)
            {
                IntPtr childHwnd = FindWindowEx(p, IntPtr.Zero, "Button", "&Next >");   //   
                Convert.ToString(childHwnd.ToInt64(), 16);
                //Console.ReadKey();
                if (childHwnd != IntPtr.Zero)
                {
                    //000809, SendMessage ， 。
                    int i = SendMessage(childHwnd, 0xF5, System.IntPtr.Zero, System.IntPtr.Zero);
                    do
                    {
                        i = SendMessage(childHwnd, 0xF5, System.IntPtr.Zero, System.IntPtr.Zero);
                    } while (i != 0);
                    //SendMessage(childHwnd, 0xF5, System.IntPtr.Zero, System.IntPtr.Zero);    //   
                }
            }

}