I know the built-in ASP.Net validators come with a client-side framework, however I've been unable to find anything that lets me check a single validator for it's Valid state.

I expect it to be possible though, so I hope someone in here knows how to do it :-)

The validator in question is a RegularExpressionValidator, which I use to determine whether an e-mail address is valid or not.

Here's some brief code:

<script>
function CheckForExistingEmail()
{
  Page_ClientValidate(); // Ensure client validation
  if (revEmail.IsValid) // pseudo code!
  {
    // Perform server side lookup in DB for whether the e-mail exists.
  }
}
</script>

<asp:TextBox runat="server" id="tbEmail" onblur="CheckForExistingEmail();" />
<asp:RegularExpressionValidator id="revEmail" runat="server" ControlToValidate="tbEmail" ErrorMessage="Not a valid e-mail address" ValidationExpression="([a-zA-Z0-9_\-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([a-zA-Z0-9\-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})" />