Using csc.exe, the C# Command-Line Compiler : Intrduction : Language Basics C# Examples

To create and run programs using the C# command-line compiler:

Enter the program using a text editor.
Compile the program.
Run the program.

Compiling the Program

Prior to running csc.exe, you may need to run the batch file vcvars32.bat, 
which is typically found in the //Program Files/Microsoft Visual Studio.NET/Vc7/Bin directory.

The name of a C# program is arbitrary
By convention, C# programs use the .cs file extension