winForm程序 屏蔽RichTextBox 的复制，粘帖，剪切 功能

 private void RichTextBox_KeyDown( object sender , KeyEventArgs e )
{
      if( e.Control && ( e.KeyCode == Keys.V || e.KeyCode == Keys.X || e.KeyCode == Keys.C ))
{
      e.Handled = true;
}
}