DJ's Blog

Well, I must have spent about an hour today trying to figure out something that I assumed would be pretty trivial, in fact it was in the end but you know how it goes.

I was creating a simple registration page for a website which requires that the user agrees to the Terms and Conditions of the site before they can submit their registration details. To begin with, I had a check box that the user would have to tick in order to state that they agreed and only when this check box was checked would the submit button be enabled, however, as I had disabled the submit button on the load of the page, all other required field validators stopped working. I assume as the submit button was disabled, ASP.NET didn't feel the need to continue wiring up the validation code necessary. So I thought that I would use one of the validation controls to ensure that the check box was checked thus no need to disable the submit button.

After a little research, I found that the CustomValidator control would do the job for me, but nearly all of the examples I found seemed to either suggest that you had to write code in your code behind/beside file to register the necessary javascript on the page which I thought was a bit odd, or they just seemed overly complex. After a little playing around with various code snippets, I came up with what I thought was rather simple and not overly complex. Shame I didn't find it in the first place, it would have saved me a fair bit of time.

To test this out, create a new web form file and add a check box to the page named "chkTandCs", then add a CustomValidator control next to it and finally a button. In the source of the web form, add the following javascript function to the head section:

<script language="javascript" type="text/javascript">
    function ValidateTandCs(source, args)
    {
        args.IsValid = document.getElementById('<%= chkTandCs.ClientID %><%= chkTandCs.ClientID %>').checked;
    }
script>

Now, modify your CustomValidator control so that it reads:

<asp:CustomValidator ID="valTandCs" ClientValidationFunction="ValidateTandCs" runat="server" ErrorMessage="Please accept Terms and Conditions before submitting.">asp:CustomValidator>