Could not load file or assembly 'System.Security.Principal.Windows'

Question

Solution has compiled successfully, but after I added an existing class file to the project, this error appeared:

The specified task executable \"csc.exe\

Answer 1

Had this same issue and resolved it.

In a 3 project solution MVC controller (Web,Business,Data)

Caused by the Microsoft.Net.Compiler 2.9.0 being installed on the Web project but not the other projects.

To resolve: Right click the solution. Manage NuGet Packages. Installed > Search for the compiler Ensure it is the same version and it is installed on all projects in your solution

Once installed my solution built successfully