C＃ - 字典 - 文件路径（Custom EqualityComparer）

问题描述

问题：自定义对象实现了EqualityComparer和IEquatable，但Dictionary并不总是使用这些方法。

上下文： / strong>我已经创建了一个助手类， FilePath 来处理文件路径，而不是将它们视为字符串。辅助类负责确定两个文件路径是否相等。然后，我需要将FilePaths存储在 Dictionary< FilePath，object> 中。

目标： strong>

  Assert.True（new FilePath（@c：\temp\file.txt）。Equals 
 new FilePath（@C：\TeMp\FIle.tXt））; 
 
 var dict = new Dictionary< FilePath，object> 
 {
 {new FilePath（@c：\temp\file.txt），new object（）} 
} 
 
 Assert.True（dict.ContainsKey（new FilePath（@ c：\temp\file.txt））; 
 
 Assert.True（dict.ContainsKey（new FilePath（@C：\TeMp\FIle.tXt））; 
  

我创建了我的FilePath类：
public class FilePath：EqualityComparer，IEquatable
{
private string _fullPath;

  public FilePath（string fullPath）
 {
 _fullPath = Path.GetFullPath（fullPath）; 
} 
 
 public override bool Equals（FilePath x，FilePath y）
 {
 if（null == x || null == y）
 return false; 
 
 return（x._fullPath.Equals（y._fullPath，StringComparison.InvariantCultureIgnoreCase））; 
} 
 
 public override int GetHashCode（FilePath obj）
 {
 return obj._fullPath.GetHashCode（）; 
} 
 
 public bool Equals（FilePath other）
 {
 return Equals（this，other）; 
} 
 
 public override bool Equals（object obj）
 {
 return Equals（this，obj as FilePathSimple）; 
} 
} 
  

问题： p>

断言1和2通过，但Assert 3失败：

 断言。 True（dict.ContainsKey（new FilePath（@C：\TeMp\FIle.tXt））; 
  

解决方案

我还需要覆盖GetHashCode（）：

  int GetHashCode（）
 {
 return _fullPath.ToLower（）。GetHashCode（）; 
} 
  

参考文献：

Problem: Custom Object implements EqualityComparer and IEquatable, but Dictionary doesn't always use these methods.

Context: I have created a helper class, FilePath for dealing with file paths instead of treating them as strings. The helper class is responsible for determining if two file paths are equal. I then need to store FilePaths in a Dictionary<FilePath, object>.

Goal:

  Assert.True(new FilePath(@"c:\temp\file.txt").Equals(
      new FilePath(@"C:\TeMp\FIle.tXt")); 

  var dict = new Dictionary<FilePath, object>
  {
      {new FilePath(@"c:\temp\file.txt"), new object()}
  }

  Assert.True(dict.ContainsKey(new FilePath(@"c:\temp\file.txt"));

  Assert.True(dict.ContainsKey(new FilePath(@"C:\TeMp\FIle.tXt"));

I've created my FilePath class: public class FilePath : EqualityComparer, IEquatable { private string _fullPath;

    public FilePath (string fullPath)
    {
        _fullPath = Path.GetFullPath(fullPath);
    }

    public override bool Equals(FilePath x, FilePath y)
    {
        if (null == x || null == y)
            return false;

        return (x._fullPath.Equals(y._fullPath, StringComparison.InvariantCultureIgnoreCase));
    }

    public override int GetHashCode(FilePath obj)
    {
        return obj._fullPath.GetHashCode();
    }

    public bool Equals(FilePath other)
    {
        return Equals(this, other);
    }

    public override bool Equals(object obj)
    {
        return Equals(this, obj as FilePathSimple);
    }
}

Question:

Assert 1 and 2 pass, but Assert 3 fails:

 Assert.True(dict.ContainsKey(new FilePath(@"C:\TeMp\FIle.tXt"));

解决方案

I needed to override GetHashCode() as well:

 public override int GetHashCode()
 {
     return _fullPath.ToLower().GetHashCode();
 }

References: What's the role of GetHashCode in the IEqualityComparer<T> in .NET?

Compiler Warning (level 3) CS0659

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