Could not load file or assembly … An attempt was m

Question

I have two projects, ProjectA and ProjectB. ProjectB is a console application, which depends on ProjectA. Yesterday, everything was working fine, but suddenly today when I run ProjectB I get this:

BadImageFormatException was unhandled:
Could not load file or assembly 'ProjectA, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. An attempt was made to load a program with an incorrect format.

Both are just regular projects, with no dependencies on any other non-.Net projects. Both are fully .Net - there is no native code, and no P/Invoke. I have other projects which depend on ProjectA and still work just fine.

Things I have tried:

• Make sure both projects are set to "Any CPU," with the build checkbox checked. They are.
• Make sure both projects are for the same Target Framework (.Net 4.0 Client Profile).
• Under ProjectB --> References --> ProjectA --> Properties, make sure "Copy Local" is set to "True" _ (I verified that ProjectA.dll is being copied correctly)
• Clean/Rebuild the solution. I even tried manually deleting the /bin and /obj folders in both projects.
• Restart Visual Studio. Restart my computer.
• Check out an entirely new copy of the repository.

But I still get the same error. I have no idea what I did to cause this, nor how to fix it. Any ideas?

Answer 1

This also can happen just by having multiple supported frameworks defined in the app.config file and, forcing the app to run in a different .NET framework other than the one mentioned first in the app.config file.

And also this fires when you have both of the mentioned frameworks available in your system.

As a workaround, bring up the target framework you are going to use for the debugging up in the app.config

ex: if you trying to run in .NET 4, config file should have something similar to this,

<supportedRuntime version="v4.0"/>
<supportedRuntime version="v2.0.50727"/>

Answer 2

Are you trying to run your .exe file from the cmd? This was my mistake. Just run the .exe file by double clicking it. If it's a .NET Core SCD for Windows 8.1/Windows Server 2012 R2 x64.

Answer 3

You might also see this issue if you're trying to package a 64bit project with an MSI installer in VS. ("The reason is because the native shim packaged with the .msi file is a 32-bit executable.")

See here for more details: http://blogs.msdn.com/b/heaths/archive/2006/02/01/64-bit-managed-custom-actions-with-visual-studio.aspx

Answer 4

I got this when building a project via Visual Studio Online (VSTS) Build using Visual Studio Build Steps.

The solution was:

• Delete the existing source folder
• Explicitly set 'Any CPU' in the platform for all Visual Studio Builds including dependencies (see screenshot below).
• Re-run the build

Answer 5

First of all I got this in VS2017 with an old project I needed to make a tiny change to and upraded all the projects to framework 4.7.

---

Several others have mentioned selecting Any CPU can fix this issue.

There's a couple places you need to do it, and it might not just be as simple as selecting from the dropdown. This fixed it for me:

1) You need to do it both here:

2) And also in Configuration Manager (right click on solution)

But what if it isn't there???

Then click New and choose these settings: (thanks @RckLN)

Answer 6

I encountered the same issue. It popped up out of the blue and that seemed strange to me.

In the Exception snapshot, for the FusionLog, I saw the following within its message:

... C:\Windows\Microsoft.NET\Framework64 ...

More about the fusion log: http://msdn.microsoft.com/en-us/library/e74a18c4(v=vs.110).aspx

All the projects had a Target CPU of AnyCPU. I changed the application project (the project that references all the other projects) to a Target CPU of x86. It now works.

Not sure how the Target CPU mix up occurred for no apparent reason, but it did.