How to get collection of all active wpf windows (multithreading) if Apllication.Current is NULL?

Question

In my project i programmatically create couple wpf windows from class in different threads. In one of this wpf windows code (xaml.cs) I want to get all active wpf windows using System.Windows.Application.Current.Windows but System.Windows.Application.Current is Null . How can i get this collection and is it really possible?

Answer 1

If you create windows on different threads for whatever reasons, you should keep track of them yourself. You could for example add them to a static collection that may be accessible from all threads, eg:

public class ApplicationService
{
    private readonly List<Window> _windows = new List<Window>();

    public IEnumerable<Window> Windows => _windows;

    public void Add(Window window)
    {
        if (window == null)
            throw new ArgumentNullException(nameof(window));

        lock (_windows)
        {
            window.Closed += Window_Closed;
            _windows.Add(window);
        }
    }

    private void Window_Closed(object sender, EventArgs e)
    {
        Window window = (Window)sender;
        lock (_windows)
        {
            window.Closed -= Window_Closed;
            _windows.Remove(window);
        }
    }
}

The Application.Current.Windows collection doesn't keep track of windows created on any other thread than the app's dispatcher thread.