C# 字典找不到 HashSet<enum> 类型的键

Question

private Dictionary<HashSet<Flags>, int> dict;

在开始时使用 Unity 检查器填充字典

public enum Flags
{
    flag1,
    flag2,
    flag3
}

迭代字典确认它包含用于访问的相同哈希集，但尝试使用密钥访问总是 returns KeyNotFoundException。使用 ContainsKey 手动测试也 returns false。

Answer 1

好吧，默认情况下 .Net 通过引用比较类，例如

// A and B has same values, but different references
var A = new HashSet<Flags>() { Flags.flag1 };
var B = new HashSet<Flags>() { Flags.flag1 };

// Not Equals, since A and B doesn't share the same reference:
if (A.Equals(B)) 
  Console.Write("Equals");
else
  Console.Write("Not Equals");

如果你想通过值进行比较，你应该实现IEqualityComparer<T>接口：

    public class HashSetComparer<T> : IEqualityComparer<HashSet<T>> {
      public bool Equals(HashSet<T> left, HashSet<T> right) {
        if (ReferenceEquals(left, right))
          return true;
        if (left == null || right == null)
          return false;

        return left.SetEquals(right);
      }

      public int GetHashCode(HashSet<T> item) {
        return item == null ? -1 : item.Count;
      }
    }

并使用它：

private Dictionary<HashSet<Flags>, int> dict = 
  Dictionary<HashSet<Flags>, int>(new HashSetComparer<Flags>());

C# 字典找不到 HashSet<enum> 类型的键

C# Dictionary can't find Key of type HashSet<enum>

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