switching to UI thread

gistfile1.txt

    public async void btnStart_Click(object sender, RoutedEventArgs e)
{
    var syncContext = SynchronizationContext.Current;
    lblStatus.Text = "Working...";
    
    // non blocking call
    var data = await GetDataFromRemoteServerAsync().ConfigureAwait(false);
    // blocking call, but runs on a worker thread
    DoSomeCpuBoundWorkWithTheData(data);
    
    // switch back to the UI thread
    await syncContext;
    lblStatus.Text = "Done";
}

    
    /// <summary>
    /// <a href="https://thomaslevesque.com/2015/11/11/explicitly-switch-to-the-ui-thread-in-an-async-method/"/></a>
    /// </summary>
    public struct SynchronizationContextAwaiter : INotifyCompletion
    {
        private static readonly SendOrPostCallback _postCallback = state => ((Action)state)();

        private readonly SynchronizationContext _context;
        public SynchronizationContextAwaiter(SynchronizationContext context)
        {
            _context = context;
        }

        public bool IsCompleted => _context == SynchronizationContext.Current;

        public void OnCompleted(Action continuation) => _context.Post(_postCallback, continuation);

        public void GetResult() { }


    }

    public static class SynchronizationContextHelper
    {
        public static SynchronizationContextAwaiter GetAwaiter(this SynchronizationContext context)
        {
            return new SynchronizationContextAwaiter(context);
        }
    }