== equals object.ReferenceEquals

Posted 2020-10-11

using System;
using System.Collections.Generic;
using System.Xml.Serialization;

class Person
{
    public int Age { get; set; }
    public string Name { get; set; }

    public static bool operator ==(Person p, Person pp)
    {
        return p.Equals(pp);
    }

    public static bool operator !=(Person p, Person pp)
    {
        return !(p == pp);
    }

    protected bool Equals(Person other)
    {
        return Age == other.Age && string.Equals(Name, other.Name);
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (ReferenceEquals(this, obj)) return true;
        if (obj.GetType() != this.GetType()) return false;
        return Equals((Person)obj);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            return (Age * 397) ^ (Name != null ? Name.GetHashCode() : 0);
        }
    }

    private sealed class AgeNameEqualityComparer : IEqualityComparer<Person>
    {
        public bool Equals(Person x, Person y)
        {
            if (ReferenceEquals(x, y)) return true;
            if (ReferenceEquals(x, null)) return false;
            if (ReferenceEquals(y, null)) return false;
            if (x.GetType() != y.GetType()) return false;
            return x.Age == y.Age && string.Equals(x.Name, y.Name);
        }

        public int GetHashCode(Person obj)
        {
            unchecked
            {
                return (obj.Age * 397) ^ (obj.Name != null ? obj.Name.GetHashCode() : 0);
            }
        }
    }

}
class Program
{
    static void Main(string[] args)
    {
        var pa = new Person() { Age = 32, Name = "zxl" };
        var pb = new Person() { Age = 32, Name = "zxl" };
        Console.WriteLine(pa == pb);//调用重载运算符==
        Console.WriteLine(pa.Equals(pb));//调用equals
        Console.WriteLine(object.ReferenceEquals(pa, pb));//比较地址

    }

}