Mastering Dynamic Loading & Localization in Silverlight Apps

1. Tips, Tricks, and Techniques for Building Killer Silverlight Apps Jeff Prosise http://www.wintellect.com/CS/blogs/jprosise/default.aspx http://twitter.com/#!/jprosise

2. Dynamic Assembly Loading • AssemblyPart class represents an assembly that's part of a Silverlight application • Assemblies typically packaged in XAPs • AssemblyPart.Load loads assemblies into appdomains at run-time • The key to dynamic assembly loading, but… • Beware the JIT compiler!

3. Loading an Assembly WebClientwc = new WebClient(); wc.OpenReadCompleted += OnOpenReadCompleted; wc.OpenReadAsync(new Uri("Widget.dll", UriKind.Relative)); . . . private void OnOpenReadCompleted(object sender, OpenReadCompletedEventArgse) { if (e.Error == null) { AssemblyPart part = new AssemblyPart(); part.Load(e.Result); } }

4. Dynamic Assembly Loading

5. Dynamic XAP Loading • XAPs can be loaded dynamically, too • Download with WebClient • Extract AppManifest.xaml from XAP and enumerate assemblies ("parts") • Extract assemblies and load with AssemblyPart.Load • Create class-library XAP by starting with Silverlight Application, not Silverlight Class Library

6. Enumerating Assemblies in a XAP StreamResourceInfosri = new StreamResourceInfo(xap, null); XmlReader reader = XmlReader.Create (Application.GetResourceStream(sri, new Uri("AppManifest.xaml", UriKind.Relative)).Stream); AssemblyPartCollection parts = new AssemblyPartCollection(); if (reader.Read()) { reader.ReadStartElement(); if (reader.ReadToNextSibling("Deployment.Parts")) { while (reader.ReadToFollowing("AssemblyPart")) { parts.Add(new AssemblyPart() { Source = reader.GetAttribute("Source") }); } } }

7. Loading Enumerated Assemblies foreach (AssemblyPart part in parts) { Stream assembly = Application.GetResourceStream (sri, new Uri(part.Source, UriKind.Relative)).Stream; part.Load(assembly); }

8. Dynamic XAP Loading

9. Dynamic Localization • Silverlight supports RESX localization • Create resource DLLs from RESX files • Resource DLLs == Satellite assemblies • Data-bind XAML elements to auto-generated ResourceManager wrapper • Two challenges • How do you switch languages at run-time? • How do you download satellite assemblies on demand rather than embed them in the XAP?

10. ObservableResources public class ObservableResources<T> : INotifyPropertyChanged { public event PropertyChangedEventHandlerPropertyChanged; private static T _resources; public T LocalizationResources { get { return _resources; } } public ObservableResources(T resources) { _resources = resources; } public void UpdateBindings() { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("LocalizationResources")); } }

11. Enumerating Satellite Assemblies StreamResourceInfosri = new StreamResourceInfo(xap, null); XmlReader reader = XmlReader.Create (Application.GetResourceStream(sri, new Uri("AppManifest.xaml", UriKind.Relative)).Stream); AssemblyPartCollection parts = new AssemblyPartCollection(); if (reader.Read()) { reader.ReadStartElement(); if (reader.ReadToNextSibling("Deployment.Parts")) { while (reader.ReadToFollowing("AssemblyPart")) { parts.Add(new AssemblyPart() { Source = reader.GetAttribute("Source") }); } } }

12. Loading Satellite Assemblies foreach (AssemblyPart part in parts) { if (part.Source.ToLower().Contains("resources.dll")) { Stream assembly = Application.GetResourceStream (sri, new Uri(part.Source, UriKind.Relative)).Stream; part.Load(assembly); } }

13. Dynamic Localization

14. Dynamic Page Loading • Navigation framework provides infrastructure for multi-page apps • Default content loader loads pages from XAP • PageResourceContentLoader • No built-in support for remote XAPs • Custom content loaders can load them from anywhere • -INavigationContentLoader

15. Do-Nothing Content Loader public class CustomContentLoader : INavigationContentLoader { private PageResourceContentLoader _loader = new PageResourceContentLoader(); public IAsyncResultBeginLoad(Uri targetUri, Uri currentUri, AsyncCallbackuserCallback, object asyncState) { return _loader.BeginLoad(targetUri, currentUri, userCallback, asyncState); } public boolCanLoad(Uri targetUri, Uri currentUri) { return _loader.CanLoad(AddFileNameExtension(targetUri), currentUri); } public void CancelLoad(IAsyncResultasyncResult) { _loader.CancelLoad(asyncResult); } public LoadResultEndLoad(IAsyncResultasyncResult) { return _loader.EndLoad(asyncResult); } }

16. Registering a Content Loader <nav:Frame x:Name="Main" Source="Home"> <nav:Frame.ContentLoader> <local:CustomContentLoader /> </nav:Frame.ContentLoader> </nav:Frame>

17. Dynamic Page Loading

18. Behaviors • Combine triggers and actions into one package • Useful when user-input events and actions taken in response to those events are tightly bound • e.g., drag behavior requires coupling of MouseLeftButtonDown, MouseMove, and MouseLeftButtonUp events • Derive from Behavior or Behavior<T> • Override OnAttached and OnDetaching • AssociatedObject property references attachee

19. Implementing a Behavior public class DisappearBehavior : Behavior<UIElement> { protected override void OnAttached() { base.OnAttached(); AssociatedObject.MouseLeftButtonDown += OnClick; } protected override void OnDetaching() { base.OnDetaching(); AssociatedObject.MouseLeftButtonDown -= OnClick; } private void OnClick(object sender, MouseButtonEventArgs e) { AssociatedObject.Visibility = Visibility.Collapsed; } }

20. Applying a Behavior xmlns:local="clr-namespace:namespace" xmlns:i="clr-namespace:System.Windows.Interactivity; assembly=System.Windows.Interactivity" . . . <Rectangle Width="300" Height="200" Fill="Red"> <i:Interaction.Behaviors> <local:DisappearBehavior /> </i:Interaction.Behaviors> </Rectangle>

21. Behaviors

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