Pascal Case
The first letter in the identifier and the first letter of each subsequent concatenated word are capitalized. You can use Pascal case for identifiers of three or more characters.
ex. ForeColor
Camel Case
The first letter of an identifier is lowercase and the first letter of each subsequent concatenated word is capitalized.
ex. foreColor
Uppercase
All letters in the identifier are capitalized. Use this convention only for identifiers that consist of two or fewer letters.
ex. System.IO
From: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/cpconcapitalizationstyles.asp