public void Insert(int index, T element)
{
if (index > Count)
{
throw new ArgumentOutOfRangeException("index");
}
root = root.InsertIntoNew(index, element);
Debug.Assert(root.IsMutable);
}
public void Add(KeyValuePair <TKey, TValue> item)
{
root = root.InsertIntoNew(item, CompareKV);
}