Most common C# bitwise operations on enums

For the life of me, I can't remember how to set, delete, toggle or test a bit in a bitfield. Either I'm unsure or I mix them up because I rarely need these. So a "bit-cheat-sheet" would be nice to have.

For example:

flags = flags | FlagsEnum.Bit4;  // Set bit 4.

or

if ((flags & FlagsEnum.Bit4)) == FlagsEnum.Bit4) // Is there a less verbose way?

Can you give examples of all the other common operations, preferably in C# syntax using a [Flags] enum?

---

I did some more work on these extensions - You can find the code here

I wrote some extension methods that extend System.Enum that I use often... I'm not claiming that they are bulletproof, but they have helped... Comments removed...

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(
                        "Could not append value from enumerated type '{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(
                        "Could not remove value from enumerated type '{0}'.",
                        typeof(T).Name
                        ), ex);
            }  
        }

    }
}

Then they are used like the following

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

---

在.NET 4中，您现在可以编写：

flags.HasFlag(FlagsEnum.Bit4)

---

The idiom is to use the bitwise or-equal operator to set bits:

flags |= 0x04;

To clear a bit, the idiom is to use bitwise and with negation:

flags &= ~0x04;

Sometimes you have an offset that identifies your bit, and then the idiom is to use these combined with left-shift:

flags |= 1 << offset;
flags &= ~(1 << offset);

链接地址: http://www.djcxy.com/p/36386.html

上一篇: 按位运算符和“字节顺序”

下一篇: 对枚举最常见的C＃按位操作