Where do I find the C# Compiler on my computer?

The C# compiler CSC.exe is found here:
  C:\Windows\Microsoft.NET\Framework\v4.0.30319\Csc.exe

This is on a Windows 8.1 Professional machine.

In any case search in this folder by changing the directory as shown below
C:/ cd %Windir%/Microsoft.NET/Framework

You may find more than one Framework on your computer
The one shown in the beginning of this post is for version 4.0.30319