C# 4.0 Pocket Reference, 3rd Edition

Enums

An enum is a special value type that lets you specify a group of named numeric constants. For example:

public enum BorderSide { Left, Right, Top, Bottom }

We can use this enum type as follows:

BorderSide topSide = BorderSide.Top;
bool isTop = (topSide == BorderSide.Top);   // true

Each enum member has an underlying integral value. By default, the underlying values are of type int, and the enum members are assigned the constants 0, 1, 2... (in their declaration order). You may specify an alternative integral type, as follows:

public enum BorderSide : byte { Left, Right, Top, Bottom }

You may also specify an explicit integral value for each member:

public enum BorderSide : byte
 { Left=1, Right=2, Top=10, Bottom=11 }

The compiler also lets you explicitly assign some of the enum members. The unassigned enum members keep incrementing from the last explicit value. The preceding example is equivalent to:

public enum BorderSide : byte
 { Left=1, Right, Top=10, Bottom }

Enum Conversions

You can convert an enum instance to and from its underlying integral value with an explicit cast:

int i = (int) BorderSide.Left;
BorderSide side = (BorderSide) i;
bool leftOrRight = (int) side <= 2;

You can also explicitly cast one enum type to another; the translation then uses the members’ underlying integral values.

The numeric literal 0 is treated specially in that it does not require an explicit cast:

BorderSide b = 0;    // No cast required
if (b == 0) ...

In this particular example, BorderSide has no member with an ...