C textbox validating event
For more information, see the WM_KILLFOCUS topic in the "Keyboard Input Reference" section, and the "Message Deadlocks" section of the "About Messages and Message Queues" topic in the MSDN library at The following code example uses the derived class Text Box and validates an e-mail address that the user enters. Length Hi Dan, Ensure that the focus is set to some other control when moving off text box control. If the focus is not on some other control than text box but you try closing the form, this event will be fired twice, since the form performs the validation again. Length Hello to all I'm handling the Validating event for one text box. If something is wrong in user input I show a warning message. Cancel=true] to method the message is displayed twice (event fired twice). If something is wrong in user input I show a warning message. Cancel=true] to method the message is displayed twice (event fired twice). There is an event Validating that can be used on Text Box that are very useful but there are also an event named Validated that I can't find much use of.
Active Control property to the current form, focus events occur in the following order: I'd suggest using the Leave because I assume you aren't validating the value, but formatting it. In that case you should also somehow tell the user that there’s a problem with the field. For example, if the user presses Tab, clicks on another control, presses Enter to trigger the Accept button, or presses Esc to trigger the Cancel button.For example, you could display an error message, change the field’s background color, or at least beep to let the user know that focus did not leave the field because something is wrong. The event triggers even if the user tries to close the form.It creates lots of problem when you have multiple text boxes on one screen and every text box has some logic written in Validate. But when the user click on Enter, he wants the Text Box to validate the change.In validate event you can control focus easily but not in Lost Focus so easily. So here is my suggestion : use the Lost Focus event and the Key Down event when the key is Enter.