protected override void DefWndProc(ref Message m)
{ 
  if (m.Msg == 0x200)
  { 
   MessageBox.Show("捕捉到消息");
  } 
  else 
  { 
  } 
  base.DefWndProc(ref m);
}

public partial class Form1 : Form 
{ 
  public Form1() 
  { 
   InitializeComponent(); 
  } 
  private void Form1_Load(object sender, EventArgs e)
  { 
  } 
  protected override void DefWndProc(ref Message m)
  { 
   if (m.Msg == 0x104) 
   { 
    m.Result = (IntPtr)333; 
    return; 
       } 
   else 
   {     
   } 
   base.DefWndProc(ref m); 
  } 
}

public Form1() 
{
 InitializeComponent();
}
[DllImport("User32.dll", EntryPoint = "SendMessage")]
private static extern IntPtr SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

private void button2_Click(object sender, EventArgs e)
{
 Process[] arrPro = Process.GetProcessesByName("WindowsFormsApplication1.vshost");
 IntPtr ip = SendMessage(arrPro[0].MainWindowHandle, 0x104, 1, 2);
}