مساعدة بسيطة؟؟

 public Form1()
  {
   InitializeComponent();
   this.TextAdd.KeyPress += new KeyPressEventHandler(keypressed);
  }

 private void keypressed(Object o, KeyPressEventArgs e)
 { // The keypressed method uses the KeyChar property to check whether the ENTER key is pressed. 
	// If the ENTER key is pressed, the Handled property is set to true, 
	// to indicate the event is handled.
   if (e.KeyChar == (char)Keys.Return)
	{ // continue here your tests
	 MessageBox.Show("aaaaaaaaa");
	 e.Handled = true;
	}
 }