LINQ区别不使用IEqualityComparer？

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();
     }
}

在另一个课程中,我尝试执行以下操作:

_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());

然而_normalizedWords,_wordRoots和_wordSubroots所有的结束与相同数量的元素,仿佛Distinct()方法不起作用或比较器被忽略.

我使用调试器检查了元素,并且有很多具有相同Root值的元素,因此应该只有其中一个_wordRoots,但事实并非如此,它们不会被删除或过滤.

为什么我Distinct()不工作？

Answer 1

为什么我的Distinct()不起作用？

因为Distinct 首先检查哈希码(因为它是一个快速检查以查看两个对象是否相等)然后调用Equals.由于您的GetHashCode实现都是相同的(并且与您的Equals方法不对应),Distinct因此无法正常工作.

更改您的GetHashCode方法以符合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();
     }
}