How to make the button always be in the application window after a wpf transition?

Question

WPF

In short, I'm making an application in wpf. Since I'm too lazy to write the exit button every time, I want to make it always on the screen. I heard from the teacher that there is some kind of element specifically for this, but I forgot the pancake

Answer 1

Everything turned out to be easy. On the main window, where we have a frame, we simply reduce it and add elements not to it, then they will always be on the form

Answer 2

Why do something that is almost always present on a regular form window? (cross in the upper right corner of the application window for win)