public void Dispose()
 {
     linkedlist = null;
     trav       = null;
     prev       = null;
 }
 public void Reset()
 {
     trav = linkedlist.head;
     prev = null;
 }
 public DoublyLinkedListEnumerator(DoublyLinkedList <T> linkedlist)
 {
     this.linkedlist = linkedlist;
     trav            = this.linkedlist.head;
     prev            = trav.prev;
 }