Today I’ve been having a few problems with the validation summary control when nested within and AJAX UpdatePanel. I have implemented an AJAX.NET Update panel on my master page wrapping all content that falls within it. When I added a validation summary control to one of the content pages I started to see a javascript error stating “’null’ is null or not an object” which wasn’t particually helpful!

After a bit of googling I came across this article explaining that the old validation controls are not compatible with the new way of registering client side script, the article explains that “WindowsUpdate will soon include a version of System.Web that can take advantage of the new APIs” however I’m yet to see this update appear! There is a link to some custom validator controls that work with partial rendering but I was not keen on changing the page so I looked for an alternative..

I eventually came across Microsoft’s Pilot program for downloadable hot fixes, the issue can be resolved easily by downloading and installing the following fix:

http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=6106

Hope this helps..