After a clean Windows reformat and installing Visual Studio 2013, trying to build a project with database-first Entity Framework edmx files yields the following error:
I give a lot of credit to Andy Mahaffey for his answer, without it I would not have found what I did. I followed along his line of research but didn't like the idea of just changing the UsingTasks' attributes. I opened up the "C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Data.Entity.targets" file and I found the first thing it says after the opening Project element is this comment:
I followed it's suggestion and presto, problems solved.
I hope this helps!
Paste the line below as the last element before the tag in the following file. C:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets