We've recently updated a fairly large ASP.NET website (~1500th alexa traffic ranking) to use VS2010 and .NET 4.0 running on Windows Server 2008 R2
Since then, when we deploy new versions of the site we occasionally noticed the same error in this post: ASP.Net cannot create/shadow copy The error message is: Cannot create/shadow copy 'xxxx, Version=4.0.4301.26898, Culture=neutral, PublicKeyToken=null' when that file already exists
However, unlike in that post, the error is occurring only in our production environments & only on some servers.
After we ship a new version of the code, we recycle all AppPools and the error starts occuring.
A further AppPool recycle seems to fix the issue, however I really want to know how we can avoid this problem in the first place?
We've finally solved our 'Cannot create/shadow copy' problems. The problem turned out to be due to the timing of our AppPool recycle & our directory copies. It worked something like this:
The problem was that our admin site was a virtual directory of the main site and used the same AppPool. This worked fine under .NET 2.0, but I think we can pinpoint the failures to when we upgraded to .NET 4.0. Seems to run just fine if we do it this way instead: