Running C#.NET from MS DOS command line

I was trying to run a program (HelloWorld) in C#.NET from DOS command line by using the following command:
csc hello.cs
However it is not working. I am getting the following message:
'cpc' is not recognized as an internal or external command,
operable program or batch file.
what am I doing wrong?

You have to use the Visual Studio command prompt, as opposed to the regular Windows command prompt, to set up the appropriate environment variables. Note that there is no DOS any more.