Standard Numeric Format Strings

"X" or "x"
Hexadecimal
Result: A hexadecimal string.
Supported by: Integral types only.
Precision specifier: Number of digits in the result string.
More information: The HexaDecimal ("X") Format Specifier.
255 ("X") -> FF
-1 ("x") -> ff
255 ("x4") -> 00ff
-1 ("X4") -> 00FF