/// <summary>
 /// insert a stringlist at specific position
 /// </summary>
 /// <param name="index"></param>
 /// <param name="collection"></param>
 public void InsertRange(int index, ListSerializable <T> collection)
 {
     if (collection != null)
     {
         using (IEnumerator <T> en = collection.GetEnumerator())
         {
             while (en.MoveNext())
             {
                 Insert(index++, en.Current);
             }
         }
     }
 }
 public void AddRange(ListSerializable <T> collection)
 {
     InsertRange(Count, collection);
 }