class Order
{
  public string OrderNumber { get; set; }
  public decimal OrderTotal { get; set; }
  public string Reference { get; set; }
}
class OrderHandler
{
  private readonly IEnumerable<Order> _orders;
  public OrderHandler()
  {
    _orders = new[]
        {
          new Order {OrderNumber = "F1", OrderTotal = 100, Reference = "Filip"},
          new Order {OrderNumber = "F1", OrderTotal = 100, Reference = "Filip"}
        };
  }
  public IEnumerable<Order> GetAllOrders()
  {
    return _orders;
  }
}

System.Threading.ManualResetEvent(false).WaitOne(2000) in GetAllOrders:
public IEnumerable<Order> GetAllOrders()
{
  System.Threading.ManualResetEvent(false).WaitOne(2000);
  return _orders;
}

<Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">
  <Grid.RowDefinitions>
    <RowDefinition Height="140"/>
    <RowDefinition Height="*"/>
  </Grid.RowDefinitions>
 
  <TextBlock x:Name="pageTitle" Margin="120,0,0,0" Text="Order System" Style="{StaticResource PageHeaderTextStyle}" Grid.Column="1" IsHitTestVisible="false"/>
  <StackPanel Grid.Row="1" Margin="120,50,0,0">
    <TextBlock x:Name="Information" />
    <ProgressBar x:Name="OrderLoadingProgress" HorizontalAlignment="Left" Foreground="White" Visibility="Collapsed" IsIndeterminate="True" Width="100">
      <ProgressBar.RenderTransform>
        <CompositeTransform ScaleX="5" ScaleY="5" />
      </ProgressBar.RenderTransform>
    </ProgressBar>
    <ListView x:Name="Orders" DisplayMemberPath="OrderNumber" />
  </StackPanel>
  <AppBar VerticalAlignment="Bottom" Grid.Row="1">
    <Button Content="Load orders" x:Name="LoadOrders" Click="LoadOrders_Click" />
  </AppBar>
</Grid>

public MainPage()
{
  this.InitializeComponent();
 
  Information.Text = "No orders have been loaded yet.";
}
private void LoadOrders_Click(object sender, RoutedEventArgs e)
{
  OrderLoadingProgress.Visibility = Visibility.Visible;
  var orderHandler = new OrderHandler();
  var orders = orderHandler.GetAllOrders();
  OrderLoadingProgress.Visibility = Visibility.Collapsed;
}

public sealed partial class MainPage : Page
{
  private BackgroundWorker _worker = new BackgroundWorker();
  public MainPage()
  {
    InitializeComponent();
 
    _worker.RunWorkerCompleted += WorkerRunWorkerCompleted;
    _worker.DoWork += WorkerDoWork;
  }
 
  void WorkerDoWork(object sender, DoWorkEventArgs e)
  {
    var orderHandler = new OrderHandler();
    var orders = orderHandler.GetAllOrders();
  }
 
  private void LoadOrders_Click(object sender, RoutedEventArgs e)
  {
    OrderLoadingProgress.Visibility = Visibility.Visible;
    _worker.RunWorkerAsync();
  }
 
  void WorkerRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
  {
    Dispatcher.BeginInvoke(new Action(() =>
    {
      // Update the UI
      OrderLoadingProgress.Visibility = Visibility.Collapsed;
    }));
  }
}

private async void LoadOrders_Click(object sender, RoutedEventArgs e)

Task<IEnumerable<Order>>.Factory.StartNew(() => { return orderHandler.GetAllOrders(); });

// Before
var orders = orderHandler.GetAllOrders();
 
// After
var orders = await Task<IEnumerable<Order>>.Factory.StartNew(() => { return orderHandler.GetAllOrders(); });

private async void LoadOrders_Click(object sender, RoutedEventArgs e)
{
  OrderLoadingProgress.Visibility = Visibility.Visible;
      
  var orderHandler = new OrderHandler();
 
  var orderTask = Task<IEnumerable<Order>>.Factory.StartNew(() =>
  {
    return orderHandler.GetAllOrders();
  });
 
  var orders = await orderTask;
 
  Orders.Items.Clear();
  foreach (var order in orders)
    Orders.Items.Add(order);
 
  OrderLoadingProgress.Visibility = Visibility.Collapsed;
}