Button validating event vb net
The Required Field Validator is actually very simple, and yet very useful.You can use it to make sure that the user has entered something in a Text Box control.An alternate solution would be to build our own control.
I'm sure that all the attributes of the controls makes sense by now, so I won't go into details about them. You should see something like this: If your browser supports Java Script, which most modern browers do, then you will notice that the page is not being posted back to the server - the validation is performed clientside! To see how it feels, you can add enableclientscript="false" to the Required Field Validator and try again.
If this attribute is not present, all the Register For Event Validation work is in vain.
The runtime does not validate events for controls that do not have the Supports Event Validation attribute present, nor does the runtime does look at the custom attributes of the control’s base class.
If the user selected the 4th option and posted the form to the server, the server would throw an exception because it didn’t know “4” was a legal value. NET know the value “4” is legal with the Register For Event Validation method of the Client Script Manager class.
Register For Event Validation must be called during the rendering phase, so we need to override a Render method.
In our example, we knew we only had one additional legal value – the value “4”.