Vb net force validating event
If you do not set the Cancel property, Windows Forms will assume that validation succeeded for that control, and raise the Validated event.For a code example that validates an email address in a Text Box, see Validating.The masking language that is used by Masked Text Box is very flexible.It allows you to specify required characters, optional characters, literal characters, such as hyphens and parentheses, currency characters, and date separators.
(See the section in this chapter entitled "Validation With Got Focus and Lost Focus Events".) In general, the best time to validate a field's contents is when the user attempts to leave the field.
If you need to require users to enter data in a well-defined format, such as a telephone number or a part number, you can accomplish this quickly and with minimal code by using the Masked Text Box control.
A is a string made up of characters from a masking language that specifies which characters can be entered at any given position in the text box. If the user types an incorrect entry, for example, the user types a letter when a digit is required, the control will automatically reject the input.
LISTING 5.4 USING THE VALIDATE EVENT PROCEDURE Private Sub txt Age_Validate(Cancel As Boolean) If Not Is Numeric(txt Age.
When users enter data into your application, you may want to verify that the data is valid before your application uses it.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.Important If you have custom validation that takes place after the Validating event, it will not affect the data binding.