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", "A"), "value 2A");
data.Add(new MyKey("1", "Z"), "value 1Z");
data.Add(new MyKey("3", "A"), "value 3A");
string myValue;
if (data.TryGetValue(new MyKey("1", "A"), 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,如果我以这种方式通过 MyKey 类更改 MyKey 结构:
public class MyKey
然后方法 TryGetValue
没有找到任何 key ,尽管 key 就在那里。
我确信我遗漏了一些明显的东西,但我不知道是什么。
有什么想法吗?
谢谢
** 解决方案 **
(请参阅接受的解决方案以获得更好的 GetHashCode 解析)
我已经像这样重新定义了 MyKey 类,现在一切正常:
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();
}
}
感谢所有回答此问题的人。
最佳答案
您需要重写 MyKey
类中的 Equals()
和 GetHashCode()
也许是这样的:
GetHashCode()
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);
}
关于C# 通用字典 TryGetValue 找不到键,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/9976224/