How to validate a custom ASP.net control before postback

Question

I've created a custom control in a class project(DLL) and am using it in a page where I have the standard ASP.net required field validator control to ensure some property of the custom control is filled by the user.

For some reason, validation only happens after postback. I need the validation to happen on the client-side before postback i.e in a similar manner to the way a standard text box is validated by the ASP.net validator controls.

Please help.

tried what? Yes I tried some ideas from the internet and none of them has helped me in this specific scenario — Yosief Kesete
have You used any Code, if u could please give the code here — Ashish Babu

user952072 user952072 · Accepted Answer · 2013-08-21T10:59:14

you can use ClientValidationFunction property of CustomValidator.

  <asp:CustomValidator id="CustomValidator1"
       ControlToValidate="Text1"
       ClientValidationFunction="ClientValidate"
       OnServerValidate="ServerValidation"
       Display="Static"
       ErrorMessage="Not an even number!"          
       runat="server"/>




<script language="javascript"> 
   function ClientValidate(source, arguments)
   {
        if (arguments.Value % 2 == 0 ){
            arguments.IsValid = true;
        } else {
            arguments.IsValid = false;
        }
   }
</script>

How to validate a custom ASP.net control before postback

3 Answers