Visual Studio displaying errors even if projects build

I have a problem with Visual Studio on a C# solution. It displays totally random errors, but the projects build. Right now, I have 33 files with errors, and I can see red squiggly lines in all of them.

I tried cleaning / rebuilding the solution, closing Visual Studio and even restarting my computer. I can modify .cs files and I see the changes in the solution.

Does anyone have an idea about why it does that?

If you have ReSharper, try emptying the ReSharper cache:

In menu, ReSharper > Options > Environment > General > Clear Caches

and disabling and re-enabling ReSharper:

In menu, Tools > Options > ReSharper > General > Suspend / Restore