/// <summary>
/// Gets the current instance of the navigator.
/// </summary>
/// <param name="navigator"></param>
/// <returns></returns>
Instance GetInstance(XPathNavigator navigator)
{
Contract.Requires <ArgumentNullException>(navigator != null);
Contract.Requires <ArgumentNullException>(navigator.UnderlyingObject != null);
Contract.Requires <ArgumentNullException>(navigator.UnderlyingObject is XObject);
Contract.Ensures(Contract.Result <Instance>() != null);
return(ModelItem.Get((XObject)navigator.UnderlyingObject).Instance);
}