C＃字典包含键 [英] C# Dictionary ContainsKey

问题描述

我的问题是ContainsKey总是返回false，即使他们的键被添加，而.Equals评估为true。

我有以下类：

  public class StatisticsFilter 
 {
 private String someString1; 
 private String someString2; 
 ..... 
 
 public override string ToString（）
 {
 return string.Format（{0}  -  {1}  -  {2}  - {3}  -  {4}，someString1，someString2，...）
} 
 
 public override bool Equals（object obj）
 {
 return obj。 。的ToString（）等于（的ToString（））; 
} 
 
 public override int GetHashCode（）
 {
返回ToString（）。GetHashCode（）; 
} 
} 
  

然后我有一个字典，如下所示： / p>

  private readonly IDictionary< StatisticsFilter，Statistics> _filteredStatisticsDict = 
 new Dictionary< StatisticsFilter，Statistics>（）; 
 
 .... 
 
 {
 //总是评估为假！ 
 if（_filteredStatisticsDict.ContainsKey（statisticsFilter）== false）
 {
 _filteredStatisticsDict.Add（statisticsFilter，new Statistics（））; 
} 
} 
  

解决方案

使用您给我们的代码进行复制。

  using System; 
使用System.Collections.Generic; 
 
 public class StatisticsFilter 
 {
 private String someString1; 
 private String someString2; 
 
 public StatisticsFilter（string x，string y）
 {
 this.someString1 = x; 
 this.someString2 = y; 
 
 
 public override string ToString（）
 {
 return string.Format（{0}  -  {1} xyz，someString1，someString2）; 
} 
 
 public override bool Equals（object obj）
 {
 return obj.ToString（）。Equals（ToString（））; 
} 
 
 public override int GetHashCode（）
 {
返回ToString（）。GetHashCode（）; 
} 
} 
 
 class Test 
 {
 static void Main（）
 {
 var dict = new Dictionary< StatisticsFilter ，int>（）; 
 
 var sf1 = new StatisticsFilter（hello，there）; 
 var sf2 = new StatisticsFilter（hello，there）; 
 
 dict [sf1] = 10; 
 Console.WriteLine（dict.ContainsKey（sf2））; //打印真
} 
} 
  

My problem is ContainsKey is always returning false even when they key has been added and .Equals evaluates to true.

I have the following class:

public class StatisticsFilter 
{
    private String someString1;
    private String someString2;
    .....

    public override string ToString()
    {
        return string.Format("{0}-{1}-{2}-{3}-{4}", someString1, someString2, ...)
    }

    public override bool Equals(object obj)
    {            
        return obj.ToString().Equals(ToString());
    }

    public override int GetHashCode()
    {
        return ToString().GetHashCode();
    }
}

I then have a dictionary that looks like this:

private readonly IDictionary<StatisticsFilter, Statistics> _filteredStatisticsDict =
            new Dictionary<StatisticsFilter, Statistics>();

....

{
    // ALWAYS EVALUATES TO FALSE!
    if (_filteredStatisticsDict.ContainsKey(statisticsFilter) == false)
    {
         _filteredStatisticsDict.Add(statisticsFilter, new Statistics());
    }
}

解决方案

Unable to reproduce with the code you've given us.

using System;
using System.Collections.Generic;

public class StatisticsFilter 
{
    private String someString1;
    private String someString2;

    public StatisticsFilter(string x, string y)
    {
        this.someString1 = x;
        this.someString2 = y;
    }

    public override string ToString()
    {
        return string.Format("{0}-{1}xyz", someString1, someString2);
    }

    public override bool Equals(object obj)
    {            
        return obj.ToString().Equals(ToString());
    }

    public override int GetHashCode()
    {
        return ToString().GetHashCode();
    }
}

class Test
{
    static void Main()
    {
        var dict = new Dictionary<StatisticsFilter, int>();

        var sf1 = new StatisticsFilter("hello", "there");
        var sf2 = new StatisticsFilter("hello", "there");

        dict[sf1] = 10;
        Console.WriteLine(dict.ContainsKey(sf2)); // Prints true
    }
}

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