Flag Enums in

About Flag Enums

To allow a single enum instance to represent multiple values (usually referred to as flags), one can annotate the enum with the [Flags] attribute. By carefully assigning the values of the enum members such that specific bits are set to 1, bitwise operators can be used to set or unset flags.

[Flags]
enum PhoneFeatures
{
    Call = 1,
    Text = 2
}

Besides using regular integers to set the flag enum members' values, one can also use binary literals or the bitwise shift operator.

[Flags]
enum PhoneFeaturesBinary
{
    Call = 0b00000001,
    Text = 0b00000010
}

[Flags]
enum PhoneFeaturesBitwiseShift
{
    Call = 1 << 0,
    Text = 1 << 1
}

An enum member's value can refer to other enum members values:

[Flags]
enum PhoneFeatures
{
    Call = 0b00000001,
    Text = 0b00000010,
    All  = Call | Text
}

Setting a flag can be done through the bitwise OR operator (|) and unsetting a flag through a combination of the bitwise AND operator (&) and the bitwise complement operator (~). While checking for a flag can be done through the bitwise AND operator, one can also use the enum's HasFlag() method.

var features = PhoneFeatures.Call;

// Set the Text flag
features = features | PhoneFeatures.Text;

features.HasFlag(PhoneFeatures.Call); // => true
features.HasFlag(PhoneFeatures.Text); // => true

// Unset the Call flag
features = features & ~PhoneFeatures.Call;

features.HasFlag(PhoneFeatures.Call); // => false
features.HasFlag(PhoneFeatures.Text); // => true

The working with enums as bit flags tutorial goes into more detail how to work with flag enums. Another great resource is the enum flags and bitwise operators page.

By default, the int type is used for enum member values. One can use a different integer type by specifying the type in the enum declaration:

[Flags]
enum PhoneFeatures : byte
{
    Call = 0b00000001,
    Text = 0b00000010
}