LINQ Distinct 不使用 IEqualityComparer？ [复制]

Question

我有以下型号：

public class Word {
      public string Original { get; set; }
      public string Normalized { get; set; }
      public string Root { get; set; }
      public string Subroot { get; set; }
      public Regex SubrootRegex { get; set; }
}

我创建了以下三个IEqualityComparer<Word>：

public class NormalizedWordComparer : IEqualityComparer<Word> {
     public bool Equals(Word x, Word y) {
          return x.Normalized == y.Normalized;
     }
     public int GetHashCode(Word obj) {
          return obj.GetHashCode();
     }
}

public class RootWordComparer : IEqualityComparer<Word> {
     public bool Equals(Word x, Word y) {
          return x.Root == y.Root;
     }
     public int GetHashCode(Word obj) {
          return obj.GetHashCode();
     }
}

public class SubrootWordComparer : IEqualityComparer<Word> {
     public bool Equals(Word x, Word y) {
          return x.Subroot == y.Subroot;
     }
     public int GetHashCode(Word obj) {
          return obj.GetHashCode();
     }
}

在另一堂课中，我正在尝试执行以下操作：

_normalizedWords = ConfigurationFacade.Words.Select(w => {
     Word word = new Word() { Original = w };
     word.Normalized = Normalize(word, _filters);
     word.Root = GetRoot(word.Normalized, ConfigurationFacade.WordRootPercentage);
     word.Subroot = GetRoot(word.Root, ConfigurationFacade.WordSubrootPercentage);
     word.SubrootRegex = null; //Complicated regex here
     return word;
}).Distinct(new NormalizedWordComparer());

_wordRoots = _normalizedWords.Distinct(new RootWordComparer());
_wordSubroots = _wordRoots.Distinct(new SubrootWordComparer());

但是，_normalizedWords、_wordRoots 和 _wordSubroots 都以相同数量的元素结束，就好像 Distinct() 方法不起作用或比较器被忽略了一样。

我用调试器检查了元素，有很多有相同的Root值，所以_wordRoots中应该只有一个，但事实并非如此，它们没有被删除或过滤.

为什么我的Distinct() 不起作用？

Answer 1

为什么我的 Distinct() 不起作用？

因为Distinct首先检查哈希码（因为这是一个快速检查两个对象可能是否相等）和然后致电Equals。由于您的 GetHashCode 实现都是相同的（并且不对应于您的 Equals 方法），因此 Distinct 无法按您的预期工作。

更改您的GetHashCode 方法以对应Equals：

public class NormalizedWordComparer : IEqualityComparer<Word> {
     public bool Equals(Word x, Word y) {
          return x.Normalized == y.Normalized;
     }
     public int GetHashCode(Word obj) {
          return obj.Normalized.GetHashCode();
     }
}

public class RootWordComparer: IEqualityComparer<Word> {
     public bool Equals(Word x, Word y) {
          return x.Root == y.Root;
     }
     public int GetHashCode(Word obj) {
          return obj.Root.GetHashCode();
     }
}

public class SubrootWordComparer : IEqualityComparer<Word> {
     public bool Equals(Word x, Word y) {
          return x.Subroot == y.Subroot;
     }
     public int GetHashCode(Word obj) {
          return obj.Subroot.GetHashCode();
     }
}