重写具有'dibs'的类型的Equals和GetHashCode

这个问题和Jon的回答让我意识到这个问题的存在，所以我很好奇，并启动了Visual Studio。

我遵循了MSDN页面的一个示例，然后创建了我自己的小示例。内容如下:

public class Person : IEquatable<Person>
{
    public string IdNumber { get; set; }
    public string Name { get; set; }
    public bool Equals(Person otherPerson)
    {
        if (IdNumber == otherPerson.IdNumber)
            return true;
        else
            return false;
    }
    public override bool Equals(object obj)
    {
        if (obj == null) 
            return base.Equals(obj);
        if (!(obj is Person))
            throw new InvalidCastException("The Object isn't of Type Person.");
        else
            return Equals(obj as Person);
    }
    public override int GetHashCode()
    {
        return IdNumber.GetHashCode();
    }
    public static bool operator ==(Person person1, Person person2)
    {
        return person1.Equals(person2);
    }
    public static bool operator !=(Person person1, Person person2)
    {
        return (!person1.Equals(person2));
    }
}

我有几个问题:

1. 如果Equals方法在处理我的自定义相等方面做得很好，为什么我必须重写GetHashCode方法?

2. 当比较下面的东西时，使用哪个比较器，等号还是GetHashCode?

.

static void Main(string[] args)
{
    Person sergio = new Person() { IdNumber = "1", Name = "Sergio" };
    Person lucille = new Person() { IdNumber = "2", Name = "Lucille" };
    List<Person> people = new List<Person>(){
        sergio,
        lucille
    };
    Person lucille2 = new Person() { IdNumber = "2", Name = "Lucille" };
    if (people.Contains(lucille2))
    {
        Console.WriteLine("Already exists.");
    }
    Console.ReadKey();
}