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In this simple example, the only candidate is the main form. To illustrate the principal, I've coded a call to the Validate method from the Click event of the form.--------Click Here to display the illustration--------(Keep in mind that this only happens when Auto Validate is Disable.)The other Validate overload passes a boolean. NET whether to check the current value of the Auto Validate property. Passing False gives the same result that you get with no parameter at all and results in the Validating and Validated events being triggered.
True checks Auto Validate so the events are not triggered. Validate(True) does not validateand Validate(False) does validate(When the Auto Validate property is Disable.)The Validate Children Method For explicit validation, Validate Children does more what I expected Validate to do.
Here's Validate Children responding to a button click.--------Click Here to display the illustration--------Validate Children is also more powerful because you can pass a parameter based on the Validation Constraints enumeration that limits which controls will actually trigger an evaluation.
The values can even be combined with a bitwise OR operation which actually results in a logical AND operation between the individual values.
By Dan Mabbutt The first Quick Tip Validation Guide defined validation as "the process of checking whether entered data is what it needs to be for the system to work correctly." And I noted in that article that: Windows form controls that have a Causes Validation property can fire a whole family of events when the focus shifts from the control.
Microsoft calls this "implicit validation" because the events are fired "implicitly" by . Microsoft refers to coding a call to the Validate or Validate Children method as "explicit validation".
If, somehow, you have managed to get to the end of this article and you still don't realize that all of these descriptions apply only when Auto Validate is set to Disable for the containing form, please be advised that they do.The previous article in this two part series focuses more on validation when Auto Validate is set to something else.Click Here to read that article and then return to this one. For example, this might come in handy if you had a two stage validation. Writeline is the fastest and easiest way to check whether that actually happens.--------Click Here to display the illustration--------There are two 'explicit' validation methods:-Validate Children Both have two overloads. The Validate Method You might think that you can trigger the execution of the Validating or Validated events by calling Validate from, for example, a Button, but you can't.Implicit validation occurs when Auto Validate for the form is set to Enable Prevent Focus Change (the default) or Enable Allow Focus Change. But each control has a Validating and Validated event with a Console. Here's a partial snippet: Private Sub Text Box1_Validating( By Val sender As Object, By Val e As System. In the first article, I noted that you can set ...... When Auto Validate is set to Disable, calling Validate does nothing, even though it might appear to 'work'.--------Click Here to display the illustration--------In this case, there are two ways to trigger the execution of the Validating and Validated events.Since the article above covers that, in this article, assume that Auto Validate for the form is set to Disable so Explict validation will be required. Writeline statements to confirm what is actually happening in the code. The first is to call Validate from the event subroutine handling the event.
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It's an old fashioned debugging technique, but it really helps me in this particular case. A call to Validate can be triggered by code elsewhere, but it still doesn't trigger the Validating and Validated events as shown below.--------Click Here to display the illustration--------The second is to call Validate from a container control where the controls that you want validated are child controls.