wpf make a child user control respond to key event raised on container window

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WPF

I'm sorry for not being precise in the subject title, but the problem is as follows

I Have A wpf Window (MainWindow.Xaml)
tab control inside the window
and a user control inside the tab control (added programmatically to the tab control)

my question is

How can i execute routedcommands bound to buttons inside the usercontrol using their input gestures?

say i have a button in the user control called btn_Save

btn_Save has the routed command CMD with keygesture Control + S

I want to execute save function when pressing (Control + S)
when the main window has the focus and the user control is not focused

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Thanks