Pre-populate Asp.net form from E-mail Link

I'm look for a way to pre-populate Asp.net form from E-mail Link. I tried several method such as:

http://www.test.com/ContactUs.aspx?CustID=123
http://www.test.com/ContactUs.aspx?ctl00$ctl00$MainContent$MainContent$CustID=123
http://www.test.com/ContactUs.aspx?ctl00_ctl00_MainContent_MainContent_CustID=开发者_如何学运维123

Our vendor is saying this should work but I'm having no luck with it. If someone can tell me what might be wrong with this or if there is another solution. This is being used for an e-mail campaign so that the user receiving the e-mail does not have to fill the form link is navigating to.

Jamal

You need to add server-side code to populate the fields from the querystring.