Question: After too hastily upgrading to EF 5.0.0.0 RC and being stuck with a .NET 4.5 project that wouldn't deploy to Windows Azure (.NET 4.0 and below), I decided to downgrade to EF 4.3.1.0.

I'm unsure of the best way to perform this type of migration but my strategy is to use "Manage NuGet Packages" identify which projects reference the package, uncheck the package from each project, install the replacement and recheck the correct projects.

Unfortunately, after doing this, my solution produced the titular "FileLoadException".

```
Could not load file or assembly 'EntityFramework, Version=5.0.0.0, Culture=neutral,        
PublicKeyToken=b77a5c561934e089' or one of its dependencies. The located assembly's 
manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

```

I searched through the solution files particularly packages.config for references to EF 5.0.0.0 RC but could find none.

Answer: 
I had similar issue with selenium:
I downgraded my selenium using NuGet and got the same error message. My solution was to remove the newer version lines from the app.config file.
I got same issue. I was getting the System.Data.Entity.Infrastructure; error which is only part of v5.0 or later. Just right click the Reference and select "Manage NuGet Package" . In the Installed Package option , uninstall the Entity FrameWork which is already installed and Install the 5.0 version. It solve the problem. I was trying manually get the System.Data.Entity reference , which was not success.