How to Perform Bitwise Operations on C# [Flags] Enums?

Use C# [Flags] enumeration to perform bit operations

Enumerations with the [Flags] attribute allow manipulation of individual bits in the underlying integer representation. This enables succinct representation of bit masks, where each bit represents a specific flag or option.

Set bit

To set a bit in the [Flags] enumeration, use the bitwise OR operator (|):

flags = flags | FlagsEnum.Bit4; // 设置位 4

Test position

To test whether a bit is set, use the bitwise AND operator (&):

bool isBit4Set = (flags & FlagsEnum.Bit4) != 0;

Toggle position

To toggle a bit (set if not set, clear if set), use the bitwise XOR operator (^):

flags = flags ^ FlagsEnum.Bit4; // 切换位 4

Clear bit

To clear bits, use the bitwise AND operator (&) and the complement of the bit mask:

flags = flags & ~FlagsEnum.Bit4; // 清除位 4

Custom extension method

For convenience, the following extension methods can be defined to simplify these operations:

public static bool Has<T>(this System.Enum type, T value) {
    return (((int)(object)type & (int)(object)value) == (int)(object)value);
}

public static bool Is<T>(this System.Enum type, T value) {
    return (int)(object)type == (int)(object)value;
}

public static T Add<T>(this System.Enum type, T value) {
    return (T)(object)(((int)(object)type | (int)(object)value));
}

public static T Remove<T>(this System.Enum type, T value) {
    return (T)(object)(((int)(object)type & ~(int)(object)value));
}

These extension methods can be used as follows:

SomeType value = SomeType.Grapes;
bool isGrapes = value.Is(SomeType.Grapes); // true
bool hasGrapes = value.Has(SomeType.Grapes); // true

value = value.Add(SomeType.Oranges);
value = value.Add(SomeType.Apples);
value = value.Remove(SomeType.Grapes);

bool hasOranges = value.Has(SomeType.Oranges); // true
bool isApples = value.Is(SomeType.Apples); // false
bool hasGrapes = value.Has(SomeType.Grapes); // false

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