public void Append(GmiddleCode Dot1)
        {
            if (Listcount == 0)
            {
                Head = Dot1;
                Tail = Dot1;
               
               
            }
            else
            {
                Tail.Next = Dot1;
                Dot1.Pre = Tail;
                Tail = Dot1;
               
            }
            Cur = Dot1;
            Listcount++;
        }
这个怎么不对，Head总指向最后一个