Could not load file or assembly 'EntityFramework' after downgrading EF 5.0.0.0 --> 4.3.1.0

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 1

After failed attempts to find references to EntityFramework in repositories.config and elsewhere, I stumbled upon a reference in Web.config as I was editing it to help with my diagnosis.

The bindingRedirect referenced 5.0.0.0 which was no longer installed and this appeared to be the source of the exception. Honestly, I did not add this reference to Web.config and, after trying to duplicate the error in a separate project, discovered that it is not added by the NuGet package installer so, I don't know why it was there but something added it.

<dependentAssembly>
  <assemblyIdentity name="EntityFramework" publicKeyToken="b77a5c561934e089" culture="neutral" />
  <bindingRedirect oldVersion="0.0.0.0-5.0.0.0" newVersion="5.0.0.0" />
</dependentAssembly>

I decided to replace this with the equivalent element from a working project. NB the references to 5.0.0.0 are replaced with 4.3.1.0 in the following:

<dependentAssembly>
  <assemblyIdentity name="EntityFramework" publicKeyToken="b77a5c561934e089" culture="neutral" />
  <bindingRedirect oldVersion="0.0.0.0-4.3.1.0" newVersion="4.3.1.0" />
</dependentAssembly>

This worked!

I then decided to remove the dependentAssembly reference for the EntityFramework in its entirety. It still worked!

I would still be interested in answers to these questions:

• What added the dependentAssembly for EntityFramework to my Web.config
• Any consequence(s) of removing these references

I'd be interested to learn.

Answer 2

I have this issue, and all I did was make sure that I was referencing the right .Net framework in all the projects then just change the web.config from

From

<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false"/>

To

<section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework" requirePermission="false"/>

All works..

Answer 3

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...