Download "XAP" Packages on Demand in Silverlight

using System;
using System.Net;
using System.IO;
using System.Windows;
using System.Windows.Controls;
using System.Reflection;
using System.Windows.Resources;

namespace XapLoader
{
    public partial class Splash : UserControl
    {
        private int downloadProgress;
        public Splash()
        {
            InitializeComponent();
            this.Loaded += new RoutedEventHandler(Splash_Loaded);
            this.SizeChanged += new SizeChangedEventHandler((Object sender,
                    SizeChangedEventArgs e)
                => { UpdateProgressBar(); });
        }

        private void Splash_Loaded(object sender, RoutedEventArgs e)
        {
            string contentUri = Application.Current.Host.Source.AbsoluteUri.Replace(
                    "XapLoader", "XapContent");

            WebClient wc = new WebClient();
            wc.OpenReadCompleted += new OpenReadCompletedEventHandler(wc_OpenReadCompleted);
            wc.DownloadProgressChanged
                += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
            wc.OpenReadAsync(new Uri(contentUri));
        }

        private void wc_OpenReadCompleted(Object sender, OpenReadCompletedEventArgs e)
        {
            Assembly assembly = LoadAssemblyFromXap("XapContent.dll", e.Result);
            object loadedContent = assembly.CreateInstance("XapContent.Main");

            App app = (App)Application.Current;
            app.ApplicationVisualRoot.Children.Clear();
            app.ApplicationVisualRoot.Children.Add((UserControl)loadedContent);
        }

        private void wc_DownloadProgressChanged(Object sender, DownloadProgressChangedEventArgs e)
        {
            downloadProgress = e.ProgressPercentage;
            UpdateProgressBar();
        }

        private void UpdateProgressBar()
        {
            rectProgress.Width = rectStandard.ActualWidth * downloadProgress / 100;
            txtProgress.Text = "Loading ... " + downloadProgress.ToString() + "%";
        }

        private Assembly LoadAssemblyFromXap(string relativeUri, Stream xapPackageStream)
        {
            StreamResourceInfo xapPackageSri = new StreamResourceInfo(xapPackageStream, null);
            StreamResourceInfo assemblySri = Application.GetResourceStream(xapPackageSri,
                new Uri(relativeUri, UriKind.Relative));
            AssemblyPart assemblyPart = new AssemblyPart();

            return assemblyPart.Load(assemblySri.Stream);
        }

    }
}