Strange black box appearing in wpf application

Question

Hi!

I am new in wpf application development. I just create a demo application and I see that the black box appearing in the top of my application. Can anyon

Answer 1

As the others have said it is a UI Debugger and can be very helpful. You don't need to go to the options menu to disable this though. There is a button that toggles it on and off in the Live Visual Tree tab.
See image UI Debugger toggle - visual studio