如何检查是否设置了标志组合的任何标志？

假设我有这个枚举：

[Flags]
enum Letters
{
     A = 1,
     B = 2,
     C = 4,
     AB = A | B,
     All = A | B | C,
}

例如检查是否AB已设置我可以这样做：

if((letter & Letters.AB) == Letters.AB)

有没有比以下更简单的方法来检查组合标志常量的任何标志是否已设置？

if((letter & Letters.A) == Letters.A || (letter & Letters.B) == Letters.B)

例如可以交换&与某事？

在 .NET 4 中，您可以使用Enum.HasFlag 方法 :

using System;

[Flags] public enum Pet {
   None = 0,
   Dog = 1,
   Cat = 2,
   Bird = 4,
   Rabbit = 8,
   Other = 16
}

public class Example
{
   public static void Main()
   {
      // Define three families: one without pets, one with dog + cat and one with a dog only
      Pet[] petsInFamilies = { Pet.None, Pet.Dog | Pet.Cat, Pet.Dog };
      int familiesWithoutPets = 0;
      int familiesWithDog = 0;

      foreach (Pet petsInFamily in petsInFamilies)
      {
         // Count families that have no pets. 
         if (petsInFamily.Equals(Pet.None))
            familiesWithoutPets++;
         // Of families with pets, count families that have a dog. 
         else if (petsInFamily.HasFlag(Pet.Dog))
            familiesWithDog++;
      }
      Console.WriteLine("{0} of {1} families in the sample have no pets.", 
                        familiesWithoutPets, petsInFamilies.Length);   
      Console.WriteLine("{0} of {1} families in the sample have a dog.", 
                        familiesWithDog, petsInFamilies.Length);   
   }
}

该示例显示以下输出：

//       1 of 3 families in the sample have no pets. 
//       2 of 3 families in the sample have a dog.