open new form, close existing wpf form c#

Source : dotprogramming.blogspot.com/2015/10/open-new-form-…

WPF Application still runs in background after closing.
My Windows Store app is still running in debug mode after I close it.
VS2012 Debugging fails on subsequent runs.
WPF Main application stops responding if a child window is being moved around.
Application doesn't exit if it creates a window which is not shown.
How main WPF window knows when secondary WPF window is closed.
When shutting down the application, not all windows are closed.