--相应的引用

       [DllImport("User32.dll", EntryPoint = "FindWindow")]

        private static extern int FindWindow(string lpClassName, string lpWindowName);

        [DllImport("User32.dll", EntryPoint = "FindWindowEx")]

        private static extern int FindWindowEx(IntPtr lpClassName, IntPtr lpWindowName, string isnull, string anniu);

        [DllImport("user32.dll", EntryPoint = "SendMessageA")]

        private static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

        private void test()

  {

            const int WM_CLOSE = 0x10;   //关闭

            const uint WM_DESTROY = 0x02;

            const uint WM_QUIT = 0x12;

            const int BM_CLICK = 0xF5;  //单击

            IntPtr Window_Handle = (IntPtr)FindWindow(null, "Microsoft Word");//查找所有的窗体，看看想查找的句柄是否存在，Microsoft Word  句柄              //

            if (Window_Handle ==IntPtr.Zero)   //如果没有查找到相应的句柄

            {

                MessageBox.Show("没有找到窗体");

            }

            else    //查找到相应的句柄

            {

                SendMessage(Window_Handle, WM_CLOSE, , );   //关闭窗体

              //  IntPtr childHwnd = (IntPtr)FindWindowEx(Window_Handle, IntPtr.Zero, null, "点击");//查找句柄中相应的按钮

              //  if (childHwnd == IntPtr.Zero)

              //  {

              //      MessageBox.Show("没有找到按钮");

              //  }

              //  else

              //  {

              //      SendMessage(childHwnd, BM_CLICK, 0, 0);   //单击这个句柄中的按钮

              //  }

            }

        }