protected void ChangeItemKey(T item, string newKey)
{
if (!this.ContainsItem(item))
{
throw Failure.CollectionElementMissing("item");
}
string keyForItem = GetNameForItem(item);
if (!CompareNames(keyForItem, newKey))
{
if (newKey != null)
{
this.AddKey(newKey, item);
}
if (keyForItem != null)
{
this.RemoveKey(keyForItem);
}
}
}