C# Bitwise Enum Operations: A Concise Cheat Sheet?

Common bit operations in C# enumerations

This article aims to help developers understand common enumeration bit operations in C#.

Question:

When doing bitwise operations in enumerations, it's always confusing how to set, clear, toggle, or test individual bits. These operations are not commonly used, so they are easy to forget. A "bit operations cheat sheet" will be very helpful.

Example:

<code class="language-csharp">flags = flags | FlagsEnum.Bit4;  // 设置第 4 位。</code>

or

<code class="language-csharp">if ((flags & FlagsEnum.Bit4) == FlagsEnum.Bit4) // 是否有更简洁的方法？</code>

Can you provide examples for all other common operations? It's better to use C# syntax and [Flags] enumerations.

Answer:

To solve this problem, some developers created extension methods that extend System.Enum and these methods are more convenient to use.

<code class="language-csharp">namespace Enum.Extensions
{
    public static class EnumerationExtensions
    {
        public static bool Has<T>(this System.Enum type, T value)
        {
            try
            {
                return (((int)(object)type & (int)(object)value) == (int)(object)value);
            }
            catch
            {
                return false;
            }
        }

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

        public static T Add<T>(this System.Enum type, T value)
        {
            try
            {
                return (T)(object)(((int)(object)type | (int)(object)value));
            }
            catch (Exception ex)
            {
                throw new ArgumentException(
                    string.Format(
                        "无法将值添加到枚举类型 '{0}'。",
                        typeof(T).Name
                        ), ex);
            }
        }

        public static T Remove<T>(this System.Enum type, T value)
        {
            try
            {
                return (T)(object)(((int)(object)type & ~(int)(object)value));
            }
            catch (Exception ex)
            {
                throw new ArgumentException(
                    string.Format(
                        "无法从枚举类型 '{0}' 中移除值。",
                        typeof(T).Name
                        ), ex);
            }
        }
    }
}</code>

These methods can be used like this:

<code class="language-csharp">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</code>

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