Enums: names for fixed sets

From magic numbers to names

// before: what is 2?
if (status == 2) { ... }

// after: the set IS the documentation
enum OrderStatus { Pending, Paid, Shipped, Cancelled }

if (status == OrderStatus.Paid) { ... }

OrderStatus.Paid is a named constant of the enum type. Under the hood each member is an int (0, 1, 2, 3 by default), but the variable's type restricts what it can hold: an OrderStatus can't silently become 42.

Casting and safety

The escape hatch is explicit casting — and C# will happily cast an out-of-range number into the enum type, because enums are thin wrappers over ints:

OrderStatus s = OrderStatus.Shipped;
int raw = (int)s;                     // 2
OrderStatus bogus = (OrderStatus)99;  // compiles! not a member

So a method receiving an enum can still receive a bogus cast value; if the set must be enforced, validate: Enum.IsDefined(typeof(OrderStatus), 99) is false. For beginners the rule that matters: use enums to name fixed sets; never rely on them to reject arbitrary ints.