WPF WindowStartupLocation=“CenterOwner” not really center, and pops all over, why?

Question

Well this question and this question are similar but no answers that work. In fact I was hoping WindowStartupLocation=CenterOwner would work...it doesn\'t. It seems to cent

Answer 1

In addition, we can use:

this.Owner = App.Current.MainWindow;

Or Application instead of App.
And place it in a child window constructor:

    public partial class ChildWindow : Window
    {
        public ChildWindow()
        {
            InitializeComponent();

            DataContext = new ChildWindowViewModel();

            this.Owner = App.Current.MainWindow;
        }
    }