How to make a WPF window be on top of all other windows of my app (not system wide)?

Question

I want my window to be on top of all other windows in my application only. If I set the TopMost property of a window, it becomes on top of all windows of al

Answer 1

I just ran into the same problem and found trouble setting the owner using MVVM without causing the app to crash in production. I have a Window Manager View Model that includes a command to open a window using the uri of the window - and I wasn't able to set the owner to App.MainWindow without the app crashing.

So - Instead of setting the owner, I bound the TopMost property of the window to a property in my Window Manager View model which indicates whether the application is currently active. If the application is active, the window is on top as I would like. If it is not active, other windows can cover it.

Here is what I added to my View Model:

 public class WindowManagerVM : GalaSoft.MvvmLight.ViewModelBase
    {
        public WindowManagerVM()
        {
            App.Current.Activated += (s, e) => IsAppActive = true;
            App.Current.Deactivated += (s, e) => IsAppActive = false;
        }

        private bool _isAppActive = true;
        public bool IsAppActive
        {
            get => _isAppActive;
            set
            {
                if (_isAppActive != value)
                {
                    _isAppActive = value;
                    RaisePropertyChanged(() => IsAppActive);
                }
            }
        }
    }

Here is the XAML that implements it (I use MVVM light with a ViewModelLocator as a static resource in my app called Locator):