C＃字典ContainsKey

Question

我的問題是ContainsKey總是返回false，即使他們的鍵已被添加和.Equals計算結果爲true。

我有下面的類：然後有一個字典，看起來像這樣

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(); 
    } 
} 

我：

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

.... 

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

Answer 1

無法重現與你給我們的代碼。

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 
    } 
} 

Answer 2

是否期待'ToString（）'成爲關鍵？我想你一定會通過改變字典聲明得到期望的結果：Dictionary<string, Statistics>

// not always be false 
if (_filteredStatisticsDict.ContainsKey(statistics.ToString() == false) 
{ 
    _filteredStatisticsDict.Add(statisticsFilter.ToString(), newStatisitcs()); 
} 

如果我理解你正在試圖完成的任務，這應該工作。 使用此方法，字典關鍵字基於過濾器的內容。