c# format() 합성형식지정

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconCompositeFormatting.asp

String.Format 메서드

http://msdn.microsoft.com/library/kor/default.asp?url=/library/KOR/cpref/html/frlrfSystemStringClassFormatTopic.asp