Upgrading from Microsoft.Practices.EnterpriseLibrary v 3.0 to v 6.0

Obviously the versions I was jumping in between are quite different, this application had not been upgraded in some time.  Taking one step at a time I decided to start by swapping out the DLLs.  I ran into a minor issue when I only modified the references for one of the projects in my solution to the new version, somehow one of the other projects rolled back the files during compile time to the previous version.  Re-updating the files and modifying the references for all the projects at once solved that issue.

But then I was presented with an odd error:

The type or namespace name 'Practices' does not exist in the namespace 'Microsoft'

It was especially confusing since intellisense and object name highlighting was detecting the presence of the namespace correctly.  After some web searching I ran into this thread, which implied that the target version of the framework I was building for needed to be newer or different then the one I was currently using.  I had yet to convert the project over so I was still compiling for version 3.5 of the framework.  I changed that to version 4.5 and was then able to build successfully.

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Unfortunately that was not the end of my problems.  I was using asp:ScriptManager in my project ( any control that references ScriptManager, such as the replacement control from the AjaxControlToolkit, will also have this issue ) and as a result when I tried running the project under the .net 4.0 web engine I got this error:

Could not load type 'System.Runtime.CompilerServices.ExtensionAttribute'....

I was unable to find a work around for that error as long as I was using the ScriptManager control.  If I removed that control then the web application worked perfectly.  Since my server only had windows 2003 on it upgrading IIS to .net 4.5 was not an option.  I finally decided to roll back from EnterpriseLibrary v6.0 to v5.0.414 and build the project for .net 4.0 instead of 4.5.

This worked well until I started getting an odd error:

Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.Data, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference.

It turned out that one of my solutions was hanging onto an old version of one of my other projects DLLs, even though the primary project was referencing the sub project in my solution apparently it did not refresh that sub projects DLL in its cache.  This was an issue since at one point I had the sub project referencing version 6.0.0.0 of the EnterpriseLibrary DLL.  I removed and re-added the primary project's reference to the sub project, the cache refreshed itself and all was well.