C# – Visual Studio 2015: Could not resolve mscorlib for target framework

The .NET Assembly loader:

• is unable to find 1.2.0.203
• but did find a 1.2.0.200

This assembly does not match what was requested and therefore you get this error.

In simple words, it can't find the assembly that was referenced. Make sure it can find the right assembly by putting it in the GAC or in the application path. Also see https://docs.microsoft.com/archive/blogs/junfeng/the-located-assemblys-manifest-definition-with-name-xxx-dll-does-not-match-the-assembly-reference.

It could be that the path to your solution is too long:

Meaning:

C:\MyProject\Folder\SubFolder...

should be Under "256 Character".

http://wcfvs.blogspot.com/2011/04/could-not-resolve-mscorlib-for-target.html

I found this thread when I had the same issue but had no reference issues. I found the link above and it solved my problem. Hopefully this will help someone else who comes here with the same problem.