C#通用字典TryGetValue找不到键

发布时间：2020-12-15 06:28:06 所属栏目：百科来源：网络整理

导读：我有这个简单的例子： using System;using System.Collections.Generic;namespace ConsoleApplication1{ class Program { static void Main(string[] args) { DictionaryMyKey,string data = new DictionaryMyKey,string(); data.Add(new MyKey("1","A"),"va

我有这个简单的例子：

using System;
using System.Collections.Generic;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Dictionary<MyKey,string> data = new Dictionary<MyKey,string>();
            data.Add(new MyKey("1","A"),"value 1A");
            data.Add(new MyKey("2","value 2A");
            data.Add(new MyKey("1","Z"),"value 1Z");
            data.Add(new MyKey("3","value 3A");

            string myValue;
            if (data.TryGetValue(new MyKey("1",out myValue))
                Console.WriteLine("I have found it: {0}",myValue );

        }
    }

    public struct MyKey
    {
        private string row;
        private string col;

        public string Row { get { return row; } set { row = value; } }
        public string Column { get { return col; } set { col = value; } }

        public MyKey(string r,string c)
        {
            row = r;
            col = c;
        }
    }
}

这工作正常但是如果我以这种方式用MyKey类更改MyKey结构：

public class MyKey

然后方法TryGetValue没有找到任何键,尽管关键是在那里.

我相信我错过了一些明显的东西,但我不知道什么.

任何想法？

谢谢

**解决方案**

(请参阅获取更好的GetHashCode解决方案的解决方案)

我已经重新定义了MyKey类,所有这一切都正常工作：

public class MyKey
{
    private string row;
    private string col;

    public string Row { get { return row; } set { row = value; } }
    public string Column { get { return col; } set { col = value; } }

    public MyKey(string r,string c)
    {
        row = r;
        col = c;
    }

    public override bool Equals(object obj)
    {
        if (obj == null || !(obj is MyKey)) return false;

        return ((MyKey)obj).Row == this.Row && ((MyKey)obj).Column == this.Column;
    }

    public override int GetHashCode()
    {            
        return (this.Row + this.Column).GetHashCode();
    }    
}

感谢所有的人回答了这个.

解决方法

您需要覆盖类MyKey中的Equals()和GetHashCode()

也许这样的事情：

GetHashCode的()

public override int GetHashCode()
{
   return GetHashCodeInternal(Row.GetHashCode(),Column.GetHashCode());
}
//this function should be move so you can reuse it
private static int GetHashCodeInternal(int key1,int key2)
{
    unchecked
    {
        //Seed
        var num = 0x7e53a269;

        //Key 1
        num = (-1521134295 * num) + key1;
        num += (num << 10);
        num ^= (num >> 6);

        //Key 2
        num = ((-1521134295 * num) + key2);
        num += (num << 10);
        num ^= (num >> 6);

        return num;
    }
}

等于

public override bool Equals(object obj)
{
    if (obj == null)
        return false;
    MyKey p = obj as MyKey;
    if (p == null)
        return false;

    // Return true if the fields match:
    return (Row == p.Row) && (Column == p.Column);
}

（编辑：李大同）

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