Chapter 4, Problem 4MQ9

Explanation of Solution

Value assigned to the e parameter’s Handled property to cancel the key pressed by the user:

If a key is pressed within a control (i.e. the control has been focused), then the KeyPress event will occur.

• The keyPress event procedure sends the pressed key’s value to the “e” parameter of the keyPress event.
  • The acceptance of pressing key has been handled by using the property “Handled”.

e.Handled

• “Handled” property contains the Boolean values “True” or “False”.
• If the “Handled” property of the control is “true”, then the control cancels the pressed keys.

  e.Handled=True

• If the “Handled” property of the control is “false”, then the control accepts the pressed keys.

e.Handled = False

Example:

The sub procedure “CancelKeys” allows the text boxes “txtCode” and “txtSales” to accept only the numbers and the backspace key...