I switched recently our asp.net 3.5 solution from VS 2008 to VS 2010 while still wanting it to be in .net 3.5 (as the deployment server runs on 3.5 only)
The libraries are migrated ok - no problems, but the web site is causing problems. The error message I get on every aspx page is like this:
D:\WebSites\.....aspx: ASP.NET runtime error: Could not load type 'Microsoft.Build.Framework.ITaskItem2' from assembly 'Microsoft.Build.Framework, Version=22.214.171.124, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.
I found out that the interface the compiler is looking for (ITaskItem2) is only available in .net 4.0, but it keeps looking for it in 3.5 assembly which is obviously wrong.
I was trying to locate where this discrepancy is originating, but with no luck.
It hinders my work significantly, because when the page is not compiled, the intellisense is not working for asp components, also debugging of the web pages is not working.
But even when this error occurs in VS, the pages are working correctly when displaying them in browser (using IIS), so this is VS-only problem.
If you have any idea, what could be wrong here, please let me know.