The problem is described here:
Due to performance considerations, the RadGridView bound to an object-relational hierarchy supports CRUD operations only for its first level.
I don't want performance but I need to write at less as possible code to achieve this. Performance isn't an issue if I can ignore manually handling of operations for next levels.
Also another related question is that does ASP.NET RadGridView act like WinForms or it can support unlimited level of CRUD operations ?