任务延迟不等待（Windows Phone 8应用程序）

Question

I'm trying to perform a really simple Task. I've started a new project using VS Express 2013, choosing a Windows Phone 8 application (instead of Silverlight). On xaml side, the interface contains one button and one rectangle. What I want to do is : when the button is clicked, the rectangle will be filled with a green background then after 1 second, the background will shift to red. Finally the text in the button is changed to "FINISHED", simply to check that everything behaved in the correct order. At first, I tried to use Thread.Sleep methods, but this "works" only with Silverlight if I understand well. So I've searched and found many different posts and I am a bit confused between Tasks, threads, TPL, etc.. Here is what I tried (located in my main)

public sealed partial class MainPage : Page
{
    public MainPage()
    {
        this.InitializeComponent();           
        this.NavigationCacheMode = NavigationCacheMode.Required;
    }

    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        // TODO: préparer la page pour affichage ici.

    }
private void BtnClick(object sender, RoutedEventArgs e)
    {
        //Task task = Task.Factory.StartNew( () => DoWait());
        DoWait();
    }

    public async void DoWait()
    {
        SolidColorBrush greenBrush = new SolidColorBrush(Colors.Green);
        SolidColorBrush redBrush = new SolidColorBrush(Colors.Red);
        BtnGreen();
        await Task.Delay(1000);
        Rect1.Fill = redBrush;
        await Task.Delay(1000);               
        LabelChange();
    }

    public void LabelChange()
    {
        Btn.Content = "FINISHED";
    }

    public void BtnGreen()
    {
        SolidColorBrush greenBrush = new SolidColorBrush(Colors.Green);
        Rect1.Fill = greenBrush;
    }

However the following happens : - The rectangle is filled with red color - There is a 1 second pause - The text in the button is changed. So, everything goes fine except the first pause (between the rectangle going green, and then red). It is as if the first "await Task.delay(1000)" is not waited after (ie I never see the rectangle changing to green).

I've tried to find an explanation but I'm totally lost... If someone could help, I'd be most grateful.

EDIT : here is a more detailed description of the problem The first time I click on the button, there is a short delay before the rectangle goes green, but when I further click on the button, the rectangle will shift to green instantaneously. So the delay (UI blocked ?) happens only the first time the button is clicked

Answer 1

Following Romasz answer, I found out my problem occured only when running the app from the emulator. When relased on the phone, everything works fine. So it was probably a problem of loading dynamic libraries.