It works exactly like when your not using Master/Detail...

Yes, you're right. But maybe I would have to ask: if I want to add registers to Master table and to Detail table, then I would have to put one Add button for Master table and another Add button for Detail table. If I click an Add button, it could call another aspx page (consuming time) or... Could it be possible to work in the same aspx page where Master/Detail tables are? I meant that kind of examples.

Just make the add procedure for the master add a blank record to the master, and add a blank record to the detail linking it to the master, and rebind the detail in editing mode ;-).