I would suggest maybe using the following overlay method instead.
Overlay XMAL:
<UserControl x:Class="WindowsPhoneSample7.OverLay"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
d:DesignHeight="800" d:DesignWidth="480">
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="400"/>
<RowDefinition Height="400"/>
</Grid.RowDefinitions>
<StackPanel Grid.Row="1">
<ProgressBar IsIndeterminate="True" Foreground="Orange" Height="50" Width="480" VerticalAlignment="Center"/>
<TextBlock Text="Wait" Foreground="Orange" HorizontalAlignment="Center"/>
</StackPanel>
</Grid>
</UserControl>
Overlay code-behind:
public OverLay()
{
InitializeComponent();
this.LayoutRoot.Height = Application.Current.Host.Content.ActualHeight;
this.LayoutRoot.Width = Application.Current.Host.Content.ActualWidth;
SystemTray.IsVisible = false; //to hide system tray
}
MainPage code-behind:
public partial class MainPage : PhoneApplicationPage
{
private Popup popup;
// Constructor
public MainPage()
{
InitializeComponent();
this.popup = new Popup();
}
private void BtnStart_Click(object sender, RoutedEventArgs e)
{
this.LayoutRoot.Opacity = 0.2;
OverLay ovr = new OverLay();
this.popup.Child = ovr;
this.popup.IsOpen = true;
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += (s, a) =>
{
Thread.Sleep(5000);
};
worker.RunWorkerCompleted += (s, a) =>
{
popup.IsOpen = false;
this.LayoutRoot.Opacity = 1.0;
};
worker.RunWorkerAsync();
}
protected override void OnBackKeyPress(System.ComponentModel.CancelEventArgs e)
{
this.popup.IsOpen = false;
}
}