XPBaseCollection is an ancestor of the XPCollection class. Use XPCollection objects in your applications to represent collections of persistent objects. See the XPCollection concept for more information.
The XPBaseCollection's implementation of the ITypedList interface limits the number of nesting levels in the object's hierarchy to four levels at design time. This is done on purpose, because in some situations, Visual Studio attempts to retrieve the full hierarchy. This leads to Visual Studio hanging if the business model has self-referencing associations.
At runtime, there is no limitation for the nesting level, and you can bind controls to any property at runtime, even if it isn't visible in the designer. Also, the end-user designer doesn't inherit this problem, and the entire hierarchy will be retrieved.