Visual Studio bug: asp:UpdatePanel could not be set on property ‘ContentTemplate’

So, I ran the Secunia Online Vulnerability inspector on my work PC and noticed there were over a dozen missing patches. I ran WindowsUpdate and had to reboot.

After rebooting, I reloaded Visual Studio 2008 and my ASP.Net project that I’m working on. I noticed that the designer was unable to render on any of my pages that had an updatePanel and the error I got was:

asp:UpdatePanel could not be set on property 'ContentTemplate'

After some googling and reading and testing, here’s how I was able to fix the problem.

  1. In your project, close any pages that have the problem. This way, when you open the project again,it won’t try to display them upon loading the solution.
  2. Exit VS2008 entirely.
  3. Get to a CMD prompt (hit WindowKey-R and type cmd [enter]) and at the DOS-like prompt, type iisreset.
  4. From Windows Explorer (hit WindowKey-E) Navigate to and delete everything from C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\[Your application name]. I actually just deleted the [Your application name] folder itself.
  5. Restart VS2008, load your solution. Now, select one of the problem files, and view with designer and hopefully, you will be all fixed up.

This problem occurred on VS2008, with SP1 installed, on a project under Framework 3.5, running on a Windows XP SP2 box, 32-bit. But I’ve heard it happens on 64-bit as well.

If this does not fix it or the problem keeps coming back, you might try this hotfix: http://code.msdn.microsoft.com/KB961864/Release/ProjectReleases.aspx?ReleaseId=2194

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Author: David (81 Articles)

David is an IT professional with over 29 years of experience (he started his career as a teenager). He has programmed in more languages and on more types of computers (and similar devices) than he can remember, including TRS-80 Model I Level 2, Commodore Vic-20, C-64 and C-128, Industrial Process Controllers, CP/M machines, and Intel 80x86+ architectures. He currently uses Microsoft .NET Framework tools and SQL Server. When he's not geeking out, he studies the Martial Art, Aikido; engages in community volunteer work; writes fiction (as well as non-fiction blogs); and does home rennovation work and is an avid and aspiring photographer. He lives in Charlotte NC, USA.

20 thoughts on “Visual Studio bug: asp:UpdatePanel could not be set on property ‘ContentTemplate’

  1. I deleted the [app] folder from the Temporary ASP.NET Files and restarted the VS 2008 Editor. And it worked.

    Thanks a mil and keep on doing the fantastic job

  2. thank you david. Your post was very helpfull!!! i was trying to figure out what was happening in my code a lot of hours.

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