How to Perform Bitwise Operations on Flags Enums in C#?

Bitwise operations of [Flags] enumeration in C#

When using flag enumerations, it is crucial to master bit operations to seamlessly manage and manipulate individual bits within the enumeration value. This cheat sheet is intended to provide a brief overview of common bit operations in C#.

Set specific bits

To set a specific bit in the [Flags] enumeration, use the bitwise OR operator (|). Consider the following example:

FlagsEnum flags = FlagsEnum.None;
flags |= FlagsEnum.Bit4; // 设置位 4

Remove specific bits

To remove a specific bit, use the bitwise AND operator and the negation of the bit. Here is an example:

if ((flags & ~FlagsEnum.Bit4) == 0) {
    // 已移除位 4
}

Toggle specific bits

To switch a specific bit to its opposite value, use the bitwise XOR operator (^).

flags ^= FlagsEnum.Bit4; // 切换位 4

Check if a specific bit is set

To determine whether a specific bit is set, use the bitwise AND operator and then compare.

if ((flags & FlagsEnum.Bit4) == FlagsEnum.Bit4) {
    // 设置了位 4
}

Additional extension methods

Extending the System.Enum class with custom methods can further simplify bit operations. Consider the following extension:

public static class EnumExtensions {

    public static bool Has<T>(this Enum type, T value) =>
        (((int)(object)type & (int)(object)value) == (int)(object)value);

    public static T Add<T>(this Enum type, T value) =>
        (T)(object)(((int)(object)type | (int)(object)value));

    public static T Remove<T>(this Enum type, T value) =>
        (T)(object)(((int)(object)type & ~(int)(object)value));
}

These methods provide convenient shortcuts for bitwise operations:

SomeType value = SomeType.Grapes;
value.Has(SomeType.Grapes); // true
value = value.Add(SomeType.Oranges);
value.Has(SomeType.Oranges); // true
value = value.Remove(SomeType.Grapes);
value.Has(SomeType.Grapes); // false

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