属性之间为什么能互点，求大咖解释解释

using System;
using System.Collections;

namespace ConsoleApp3
{
    class Program
    {
        static void Main()
        {
            var list1 = new LinkedList();
            list1.AddLast(2);
            list1.AddLast(4);
            //list1.AddLast("6");

            foreach (int i in list1)
            {
                Console.WriteLine(i);
            }
        }
    }

    public class LinkedListNode
    {
        public LinkedListNode(object value) => Value = value;

        public object Value { get; }

        public LinkedListNode Next { get; internal set; }
        public LinkedListNode Prev { get; internal set; }
    }

    public class LinkedList : IEnumerable
    {
        public LinkedListNode First { get; private set; }
        public LinkedListNode Last { get; private set; }

        public LinkedListNode AddLast(object node)
        {
            var newNode = new LinkedListNode(node);
            if (First == null)
            {
                First = newNode;
                Last = First;
            }
            else
            {
                Last.Next = newNode;
                Last = newNode;
            }
            return newNode;
        }

        public IEnumerator GetEnumerator()
        {
            LinkedListNode current = First;
            while (current != null)
            {
                yield return current.Value;
                current = current.Next;
            }
        }
    }
}

互点？看了你的代码，Last它是一个链表形式的数据结构。