SharePoint 2010 – Code Build Issue: Could not load assmebly

If you are in the process of upgrading code from MOSS 2007 to SharePoint 2010 and you are trying to build the old projects, you might receive errors stating that the assemblies: Microsoft.SharePoint.AdministrationOperation and others cannot be loaded. This is due to the fact that the entries in web.config or any other files in the solution are referring to the old references: In order to fix the issue, you can replace all the 12.0 references in the solution to 14.0 and that should take care of it.