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 the same issue when updating an older project. Here's what I did to resolve it:

* Converted all projects to .NET 4.5.
* Uninstalled the NuGet package for Entity Framework 5.
* Reinstalled the NuGet package for Entity Framework 5.
* Cleaned the solution.
* Rebuilt the solution.

The projects that used Entity Framework 5 and .NET 4 were installing the Entity Framework dll version 4.4. Once I switched the .NET version to 4.5 on the project, the dll version would be 5.

My problem came from older projects being on .NET 4 and a newer project running .NET 4.5 so there were 2 dll versions of EF in my solution.

Hope this helps someone...
While Building a Project, if in the project properties it shows that it is build under Target.NET Framework 4.5, update it to 4.6 or 4.6.1. Then the build will be able to locate Entity Framework 6.0 in the Web.config file. This approach solved my problem. 
[Selecting Target framework from Project Properties](http://i.stack.imgur.com/KUFTe.png)