C# compiler Console Application question ?

I am currently using notepad with the C# compiler to make console applications. I tried to use to use the {Math.Pow} and {Math.Sqrt} methods but the console keeps giving me an error saying " 'Math' doesn't exist in the current context". I used the same code on Visual Studios console application and it works just fine. So what can be the problem ? Is there another way to get a square root of a number on a console application ? Thanks for any help !