I inherited a .NET framework 4.6 web application. When I press F5 to run it I get a CS5001(Program does not contain a static 'Main' method suitable for an entry point).

There's Program.cs in the root directory that contains a:

public static void Main(string[] args)

so it must be something with the config or some file references are messed up.

Visual Studio says that the CS5001 is occurring on line 1 of the CSC file.

How would you approach uncovering what the issue is?