public void Add(T data)
 {
     if (Head == null)
     {
         SetVeryFirstElement(data);
     }
     else
     {
         var item = new DoublyItem <T>(data);
         Tail.NextCell = item;
         item.PrevCell = Tail;
         Tail          = item;
     }
     Count++;
 }
 public void Add(T data)
 {
     if (Count == 0)
     {
         SetVeryFirstElement(data);
     }
     else
     {
         var item = new DoublyItem <T>(data)
         {
             NextCell = Head,
             PrevCell = Head.PrevCell
         };
         item.PrevCell.NextCell = item;
         Head.PrevCell          = item;
     }
     Count++;
 }
 private void SetVeryFirstElement(T data)
 {
     Head          = new DoublyItem <T>(data);
     Head.NextCell = Head;
     Head.PrevCell = Head;
 }