arithmetic operations on enum values

Question

What arithmetic operations are supported on c# enums? Surprisingly, I was unable to find it via neither google, nor wikipedia and stackoverflow.

Can I add two enum values without any cast ? Add arbitrary constant to a value or subtract it? Or does enum guarantee that a value of that type is always one of the defined enum values or their bitmask?

class ... {...
enum WeekDays : byte { Sun = 1, Mon = 2, Tue = 3, /* and so on*/ Sat = 7 };
public static bool IsWeekend (WeekDays _d) {
/// Can I be sure here that _d has value from 1..7? May it be any of 0..255?
}

I know about bitwise operations, It seems reasonable to support them for representing flags.

Wikipedia tells us, my sample also allows _d - 1 or WeekDays.Tue - WeekDays.Mon , that can be useful for strictly ordered sequential enums, but I cannot find any standard reference, could you, please, point me?

Answer 1

The following operators can be used on values of enum types: == , != , < , > , <= , >= , + , - , ^ , & , | , ~ , ++ , -- , sizeof .

Answer 2

If you want to use an arithmetic operations, do not use enums , use numbers . Enums is a naming convension for numeric values to make them more human readable and allow having a combination of them. That is actually the reason that you didn't find anything about that on internet, cause it's not soemthing that should be done with enums .