With a great hope I write you this letter, for a problem, that I have with the control validating.
The problem concern the example in the in the Chapter 13, the Title "The Textbox Control", and subtitle "Textbox Events", where we have the explications of the events of the textbox and how use them. After this subtitle "Textbox Events", in the book I have an example with copy of screens in design mode and the examples of code for textbox event "Validating". Just in this example (I write the code of the book here) I have the proposition of using "e.Cancel = true".


The code :

//////////////////////////////////////////////////////

private void txtBoxEmpty_Validating(object sender,
                                   System.ComponentModel.CancelEventArgs e)
{
  // We know the sender is a TextBox, so we cast the sender object to that
  TextBox tb = (TextBox)sender;

  // If the text is empty we set the background color of the
  // Textbox to red to indicate a problem. We use the tag value
  // of the control to indicate if the control contains valid
  // information.
  if (tb.Text.Length == 0)
  {
     tb.BackColor = Color.Red;
     tb.Tag = false;

     // In this case we do not want to cancel further processing,
     // but if we had wanted to do this, we would have added this line:
     // e.Cancel = true;
  }
  else
  {
     tb.BackColor = System.Drawing.SystemColors.Window;
     tb.Tag = true;
  }

  // Finally, we call ValidateAll which will set the value of
  // the OK button.
  ValidateAll();
}


//////////////////////////////////////////////////////


In my version of the book it is on the page 348 (“Beginning C#” – 2001 Wrox Press ISBN 1861004982), in the other version it may be on the page 358.

Finally when I do this modification proposed by You, I can’t close the form with the Top Right X button, it fires the event Validating of the Textbox. Even when I change the property CausesValidation of the form to false, it’s no effect.

I hope that this problem is not a bug of the software, and that you can find the solution.

Thanks.

Problem:
  "...Validating Event and Sticky Forms the Validating event also fires when you close
  a form. If you set the Cancel property of the CancelEventArgs object to true inside
  this event, it will cancel the close operation as well. "..
  (Quoted from: http://www.examcram2.com/articles/ar...30936&seqNum=6)

  The closing operation can be conducted in one of three ways:
  Either 1) Clicking a cancel button, 2) Window close button or 3) Escape key.


Solution:
 We now show how to stop the validation from occuring in case of canceling the operation. We
 refer to each of the possible operations specified above.


1. Cancel Button:
  Simply set the CausesValidation of the cancel button to false . Thus, every control that
  is assigned to a validating event will not be called.

2. Window close button:
  Need to override the wndProc method, check the window msg and if the last equals WN_CLOSE, and define it somewhere (it is not automatically defined) ,
  set the CausesValidation of the active control to false.
  e.g.
  protected override void WndProc(ref Message m)
  {
 if (m.Msg == WM_CLOSE)
 {
  ActiveControl.CausesValidation = false;
        }
        base.wndProc (m);
  }

3. Escape key:
 Derive a class from System.Windows.Forms.Button where you override the IButtonControl.PerformClick
  method.
  e.g.

  public class CancelButton : Button, IButtonControl
  {
  void IButtonControl.PerformClick()
 {
  this.Parent.ActiveControl.CausesValidation = false;
  base.PerformClick();

 }
  }
and use it as your form's cancel button

This about it. Do hope was of help.