The Validate event fires whenever the user attempts to set focus to another field on the same form or when the form unloads from memory while the current field has focus.

A programmer can evaluate the state of the data at that point and react to any error in the data either by: Listing 5.4 illustrates the use of the Validate event procedure to perform validation and to decide whether or not to keep focus on the current control.

The exact sequence of the events depends on whether the keyboard or the mouse is used to change the focus: Not all of these events will fire all the time. With a simple form consisting of a Combo Box and a Button, everything looks normal:--------Click Here to display the illustration--------But if the Combo Box is the only control in the form, it doesn't look so normal anymore. Regular Expressions Public Class Validation Ex Form Private Sub txt Zip Code In_Validating( By Val sender As Object, By Val e As System. (Validated and Lost Focus with the keyboard.) It can also cause a real problem.

vb prevent focus change textbox validating-22vb prevent focus change textbox validating-54

Text = "") End Sub Now consider the corresponding VB. If the end user clicks on a different control and Text1 contains an empty string, the Lost Focus event resets the background color to white, then the Validate event cancels the focus shift, and finally the Got Focus event changes the background color to yellow again. If this is the case, the converted code might fail or behave unexpectedly.

In such cases, you can force the controls in the support library to behave more closely to the original VB6 controls by setting the VB6Config.

(In my own testing, I've discovered that different events are triggered while debugging in single-step mode. Write Line is a lot more foolproof.)--------Click Here to display the illustration--------For Windows Forms, validation is normally done in the Validating event. One way to solve this problem is to add this code in the Form Closing event.

If you don't care if later events are fired, it might be easier to simply not code the e. Or, you can set the Auto Validate property to Enable Allow Focus Change.

Back Color = vb Yellow End Sub Private Sub Text1_Lost Focus() Text1.

Back Color = vb White End Sub Private Sub Text1_Validate(Cancel as Boolean) Cancel = (Text1. In some applications, however, the code in the Text1_Lost Focus method might depend on some variable that has been set in the Validate event.

By Dan Mabbutt Validation is the process of checking whether entered data is what it needs to be for the system to work correctly. This Quick Tip is the first of two that show you how to tell . Acres of code are usually devoted to validation and there is no universal 'right' way to do it.

You have to figure out what your app needs and write the code to detect it. NET gives you the tools that allow you to place code where it will do the job and then calls it. If you ask users to enter the Zip Code, you should make sure that they don't enter their last name instead.

Web pages have a special problem with validation because the entire form is sent to the server.