non-blocking async

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace asyncTest
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private async void MainWindow_OnLoaded(object sender, RoutedEventArgs e)
        {
            var cts = new CancellationTokenSource();
            Closing += delegate { cts.Cancel(); };
            await CheckToClose(cts.Token);
        }

        public async Task CheckToClose(CancellationToken ct)
        {
            while (!ct.IsCancellationRequested)
            {
                try
                {
                    await Task.Delay(TimeSpan.FromSeconds(1), ct);
                }
                catch (TaskCanceledException)
                {
                    return;
                }

                Debug.WriteLine("checking DB");
                var keepRunning = !await ShouldKeepRunning(ct);
                if (!keepRunning)
                {
                    Close();
                    return;
                }
            }
        }

        public async Task<bool> ShouldKeepRunning(CancellationToken ct)
        {
            await Task.Delay(TimeSpan.FromSeconds(5)); // simulate a long running db task
            return chkAllowClose.IsChecked.GetValueOrDefault(false);
        }
    }
}