Question

I have three textboxes on an asp.net webform, how/can I use a required field validator to ensure that at least one of them contains text?

Answer 1

I would use a CustomFieldValidator like this:

<asp:CustomValidator runat="server"
         ID="MyCustomValidator"
         ValidationGroup="YOUR_VALIDATION_GROUP_NAME"
         OnServerValidate="MyCustomValidator_ServerValidate"
         ErrorMessage="At least one textbox needs to be filled in." />

and then in your codebehind you have:

protected void MyCustomValidator_ServerValidate(object source, ServerValidateEventArgs args)
{
     if (/* one of three textboxes has text*/)
         args.IsValid = true;
     else
         args.IsValid = false;
}

You can also add a Client-side component to this validation, and make it sexy by extending it with AJAX toolkit’s ValidatorCalloutExtender control.