Check out String.Format. It accepts your variable and a format string, so you can format it as a string any way you want.
Quote:
You can format numeric results by using the String.Format method, or through the Console.Write method, which calls String.Format. The format is specified using format strings. The following table contains the supported standard format strings. The format string takes the following form: Axx, where A is the format specifier and xx is the precision specifier. The format specifier controls the type of formatting applied to the numerical value, and the precision specifier controls the number of significant digits or decimal places of the formatted output.