private void SetHeadItem(T data)
        {
            var item = new DuplexItem <T>(data);

            Head  = item;
            Tail  = item;
            Count = 1;
        }
        public void PushFront(T data)
        {
            if (Count == 0)
            {
                SetHeadItem(data);
                return;
            }

            var item = new DuplexItem <T>(data);

            item.Previous = Head;
            Head.Next     = item;
            Head          = item;
            Count++;
        }
        public void PushBack(T data)
        {
            if (Count == 0)
            {
                SetHeadItem(data);
                return;
            }

            var item = new DuplexItem <T>(data);

            item.Next     = Tail;
            Tail.Previous = item;
            Tail          = item;
            Count++;
        }
 public T PopFront()
 {
     if (Count > 0)
     {
         var result  = Head.Data;
         var current = Head.Previous;
         current.Next = null;
         Head         = current;
         Count--;
         return(result);
     }
     else
     {
         return(default(T));
     }
 }
 public T PopBack()
 {
     if (Count > 0)
     {
         var result  = Tail.Data;
         var current = Tail.Next;
         current.Previous = null;
         Tail             = current;
         Count--;
         return(result);
     }
     else
     {
         return(default(T));
     }
 }