等待异步获得价值Windows Phone 7

Question

I have problem with logging operation in WP7. When I click LogInButton it doesn't gets value to prompt = e.Result in proxy. What can I do to wait until async call is ended? I though about Thread. Sleep but i suppose it isn't able to do in WP 7.

namespace WP7App
{
 public partial class MainPage : PhoneApplicationPage
{
    bool prompt;
    // Constructor
    public MainPage()
    {
        InitializeComponent();
    }
    // login operation
    private void Log(string username, string passwd)
    {
        Service1Client proxy = new Service1Client();
        proxy.LogInCompleted += new
        EventHandler<LogInCompletedEventArgs>(proxy_LogInCompleted);
        proxy.LogInAsync(username, passwd);

    }
    public void proxy_LogInCompleted(object sender, LogInCompletedEventArgs e)
    {
        prompt = e.Result;              
    }
    //button action
    void LogInButton_Click(object sender, RoutedEventArgs e)
    {
        if (LoginBox.Text == null) { MessageBox.Show("please fill login box"); }
        if (PasswdBox.Password == null) { MessageBox.Show("enter your password"); }
        string login = LoginBox.Text;
        string passwd = PasswdBox.Password;            
        Log(login, passwd);
        if (prompt == true)
        {
            NavigationService.Navigate(new Uri("/Pages/MainLogged.xaml", UriKind.Relative));
        }
        else
        {
            MessageBox.Show("logging failed");
        }
    }                            
}

}

Answer 1

The only thing you should do is just provide user information, that some operation is still running.

If you really need that (the operation result is necessary for application) it can be done in a way, that blocks user from making another operations (like a fullscreen panel which should be shown just before starting async operation and closed when it's completed).