Create child window with WPF

I'm trying to create a daughter window that gets tied to the main window (in WPF). After creating the child window, I initialize it with nomeDaJanela.Show() . However the window becomes loose, as if it were not part of the main window, even seeming a standalone application. I would like to "lock" the main window, so if I minimize or close the main window the same thing happens to it, as it will only be accessible if it has the main window as the background.