C# 字典包含密鑰

Question

我的問題是 ContainsKey 始終返回 false，即使它們已添加並且。Equals 評估為 true。

我有以下 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();
    }
}

然后我有一個看起來像這樣的字典：

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

無法使用您提供給我們的代碼進行重現。

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

期望 'ToString()' 是關鍵嗎？ 我認為您將通過將 Dictionary 聲明更改為： Dictionary<string, Statistics>來獲得所需的結果

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

如果我了解您要完成的工作，那應該可以。 使用此方法，字典鍵基於過濾器的內容。