GroupJoin() 中有一个重载方法参数包含 IEqualityComparer<Tkey> ,有没有大佬解释一下这个 IEqualityComparer 实现类的原理，想问IEqualityComparer实现类中的Equals方法参数x和y到底代表什么，下面这个例子是我的个人理解截图和官网给出的Groupjoin()重载截图，但是对于Groupjoin()中的IEquality真的看不懂，和例子完全不一样,因为Equals()中的参数x和y的值每次都是相等的,这样有什么比较的意义，请大佬解释一下原理，不胜感激！！！

internal class Park : IEqualityComparer<Park>
{
        public double ticketPrice { get; set; }
        public string address { get; set; }
        public int peoples { get; set; }

        public bool Equals(Park x, Park y)    //比较x和y对象是否相同，按照地址比较
        {
            return x.address == y.address;
        }

        public int GetHashCode(Park obj)
        {
            return obj.ToString().GetHashCode();
        }
 }

    internal class Program
    {
        private static void Main(string[] args)
        {
            List<Park> parks = new List<Park>(){
                new Park { ticketPrice = 11, address = "天堂", peoples = 1000 },
                new Park { ticketPrice = 11, address = "天堂", peoples = 1000 },
                new Park { ticketPrice = 55, address = "南京", peoples = 85 },
                new Park { ticketPrice = 85, address = "北京", peoples = 75 },
                new Park { ticketPrice = 78, address = "多伦多", peoples = 100 },
        };
//个人理解
//第一个元素默认加入distinctList的去重数组里，调用上面的Equals方法（参数x为当前元素，y为distinctList中的元素）遍历distinctList,不存在当前元素则把该元素加入distinctLsit,最后两个`address`为天堂的元素只输出一次
            var diff = from c in parks.Distinct(new Park())
                       select c;

            foreach (var item in diff)
            {
                Console.WriteLine(item.address);
            }