Question

鉴于以下示例，我如何在第二个示例中使clientList包含5个客户端？

我希望list.Contains()方法只检查FName和LName字符串，并在检查相等性时忽略年龄。

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

Answer 1

创建一个实现IEqualityComparer的类，并在list.contains方法中传递该对象

Answer 2

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

Answer 3

覆盖结构中的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();
    }
}

此实现处理所有边缘情况。

阅读this question，了解为什么还要覆盖GetHashCode()。

Answer 4

假设您使用的是C＃3.0或更高版本，请尝试以下方法：

（以下代码未经过测试，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);
    }
}

如何实现一个平等方法？

4 个答案: