I forgot to update this to say downgrading Unity fixed my problem.
However, that looks like a different error to the one I received, waqarm22. I'm not very experienced with VS/C# errors, but that looks like it's looking for a file that isn't there? The first thing I'd try and do would be delete all the usings, and only add in the ones you really need. Also, you might have accidentally added a reference to your project that doesn't exist any more.
However, that looks like a different error to the one I received, waqarm22. I'm not very experienced with VS/C# errors, but that looks like it's looking for a file that isn't there? The first thing I'd try and do would be delete all the usings, and only add in the ones you really need. Also, you might have accidentally added a reference to your project that doesn't exist any more.