Answer by Bojan for Could not find a part of the path ... bin\roslyn\csc.exe

• Right click on your project and select Manage Nuget Packages
• Find "Microsoft.CodeDom.Providers.DotNetCompilerPlatform"
• Simply Update to an older or newer version (doesn't matter which), and then update again back to your original version.

This re-installs all the dependencies and files of the package (like csc.exe)