Indexing Service causes strange Access Denied errors in ASP.NET

A couple of weeks ago, I installed a trial copy of the Dundas .NET charting controls to play with in ASP.NET. It’s actually pretty cool, but I was attempting to show it to someone on my laptop when it stopped working.

I kept getting error messages about “Access Denied” and pointing at an unrelated line in machine.config.

It turns out that, contrary to my cursing, it wasn’t Dundas’ fault. I got the same message when attempting to use one of my own class libraries just now.

It’s a known problem, and is discussed in the Microsoft Knowledge Base under the snappy title of PRB: Access Denied Error When You Make Code Modifications with Index Services Running.

So, if you get this error, turn off Indexing Service. Alternatively, if you’re actually using it, stop it from poking around in the “Temporary ASP.NET Files” directory.