如何实现一个相等方法

本文关键字：一个 方法 实现 何实现 | 更新日期: 2023-09-27 18:01:28

给出下面的例子，我如何在第二个例子中使clientList包含5个客户端?

我希望list.Contains()方法只检查FName和LName字符串，并且在检查是否相等时忽略年龄。

struct client
{
    public string FName{get;set;}
    public string LName{get;set;}
    public int age{get;set;}
}

示例1:

List<client> clientList = new List<client>();
for (int i = 0; i < 5; i++)
{
    client c = new client();
    c.FName = "John";
    c.LName = "Smith";
    c.age = 10;
    if (!clientList.Contains(c))
    {
        clientList.Add(c);
    }
}
//clientList.Count(); = 1

示例2:

List<client> clientList = new List<client>();
for (int i = 0; i < 5; i++)
{
    client c = new client();
    c.FName = "John";
    c.LName = "Smith";
    c.age = i;
    if (!clientList.Contains(c))
    {
        clientList.Add(c);
    }
}
//clientList.Count(); = 5

如何实现一个相等方法

创建一个实现了IEqualityComparer的类，并在list中传递对象。包含方法

public class Client : IEquatable<Client>
{
  public string PropertyToCompare;
  public bool Equals(Client other)
  {
    return other.PropertyToCompare == this.PropertyToCompare;
  }
}

在你的结构中覆盖Equals和GetHashCode:

struct client
{
    public string FName { get; set; }
    public string LName { get; set; }
    public int age { get; set; }
    public override bool Equals(object obj)
    {
        if (obj == null || !(obj is client))
            return false;
        client c = (client)obj;
        return
            (string.Compare(FName, c.FName) == 0) &&
            (string.Compare(LName, c.LName) == 0);
    }
    public override int GetHashCode()
    {
        if (FName == null)
        {
            if (LName == null)
                return 0;
            else
                return LName.GetHashCode();
        }
        else if (LName == null)
            return FName.GetHashCode();
        else
            return FName.GetHashCode() ^ LName.GetHashCode();
    }
}

这个实现处理所有的边缘情况。

阅读这个问题，了解为什么你也应该覆盖GetHashCode()。

假设您正在使用c# 3.0或更高版本，请尝试这样做:

(下面的代码没有经过测试，但应该是正确的)

List<client> clientList = new List<client>();
for (int i = 0; i < 5; i++)
{
    client c = new client();
    c.FName = "John";
    c.FName = "Smith";
    c.age = i;
    var b = (from cl in clientList
             where cl.FName = c.FName &&
                   cl.LName = c.LName
             select cl).ToList().Count() <= 0;
    if (b)
    {
        clientList.Add(c);
    }
}
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