To create a client-side validation function, first add the server-side validation function described earlier.Next, add the client-side validation script function to the page.If you are using Visual Basic, the function must be in the form: control.The Custom Validator control allows you to create a validation control with customized validation logic.I agree with the need for it, as radio buttons cannot be de-selected like checkboxes can.If you're looking to roll a custom validator, it sounds like you either do it server side, at which point you can do whatever logic you want in the code behind.
I created a validator that requires that the user enters a value for the dropdown, and if they select "other / see comments" then it requires that something is in comments. Note that validation error messages do not display until you have updated one of the controls or try to submit.
The result of the validation is then stored in the Is Valid property of the Server Validate Event Args object.
You can use this method to create complex validations.
One thing that I found is that I needed to add the code to the end of an ascx control, or next to the end of the form tag in an aspx page.
control allows you to create a validation control with customized validation logic.