progress bar isinderminate=true not working when its visibility is hidden

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C#

WPF

Firstly my progressbar is hidden. then on a button click i want to show progress bar with isinderminate=true. Then again on a button click hide the progressbar.
But on running the code progressbar is not visible at all.

code:-
button1 click

pr1.Visibility=Visibility.Visible;
pr1.IsIndeterminate=true;

button2 click

pr1.Visibility=Visibility.Hidden;
pr1.IsIndeterminate=false;