[C#] string format specifiers.

Format Specifier	Description
C or c	Formats the string as currency. Precedes the number with an appropriate currency symbol ($ in the US). Separates digits with an appropriate separator character (comma in the US) and sets the number of decimal places to two by default.
D or d	Formats the string as a decimal. Displays number as an integer.
N or n	Formats the string with commas and a default of two decimal places.
E or e	Formats the number using scientific notation with a default of six decimal places.
F or f	Formats the string with a fixed number of decimal places (two by default).
G or g	General. Formats the number normally with decimal places or using scientific notation, depending on context. If a format item does not contain a format specifier, format G is assumed implicitly.
X or x	Formats the string as hexadecimal.

Reference: Visual C#® 2005: How to Program, Second Edition