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Stephen Kennedy Silverlight 3 Deep Dive


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  • Introduced in .NET 3.5 SP1, further support in .NET 4.0 Allows you to annotate your classes with what it means for an instance to be valid Place it on properties When value is set, annotations get evaluated and an exception is thrown if they fail Silverlight 3 controls automatically react to exceptions and display an error state (a visual state)
  • Note the order is important
  • Transcript

    • 1. SMTC
      SNS, EndndjHsmnwmd
      August 29, 2007
      Silverlight 3 Best Practice Do’s and Don’ts
    • 2. Stephen Kennedy (
    • 3. Design Patterns
    • 4. Design patterns
      Silverlight 3
    • 5. Model View Controller/Presenter Pattern
      Problem: Decoupling data display logic from the business logic that maintains and updates it
      Solution: MVC Pattern separates the modeling of the domain, presentation, and actions based on user input into three separate classes:
      Manages behavior/data of the application domain
      responds to requests for information about its state (usually from View)
      responds to instructions to change its state (usually from Controller).
      Manages the display information
      Informs the Model to change its state by interpreting inputs from keyboard, mouse and external instructions.
    • 6. Developed by Martin Fowler, and is an extension of MVP
      Again, the View is separated from its behavior and state
      A Presentation Model is introduced, which acts as an abstraction of the view – so the view is merely a rendering of the Presentation Model
      View has a reference to Presentation Model, but Presentation Model has no reference to view
      Presentation Model
    • 7. MVP/MVC nice for web and thick client
      Good for ASP.NET,WinForms, WPF (as a start)
      Good for Silverlight as a start
      What you’re used to
    • 8. Identical to Presentation Model, but engineered by John Gossman to utilize WPF Dependency Properties and Commands to bind UI to abstraction
      Ideal as it allows abstraction, called the ViewModel, to be tested
      Also allows for any UI to bind to ViewModel fields to show and modify the data
      XAML controls / Elements bind to properties in the ViewModel class
      Use Model-View-ViewModel Pattern
    • 9. Model
      POCO – no Dependency Properties / Routed Events
      No UI knowledge - pure data
      Design Patterns: MVVM
    • 10. View Model
      No knowledge of the view
      Exposes the model(s) / custom properties used in the view
      Use ObservableCollection<T> for collections of data
      Implement INotifyPropertyChanged for custom properties
      Should be able to act as a command line interface to the view
      No Dependency Properties
      Design Patterns: MVVM
    • 11. View
      Binds to the ViewModel (DataContext)
      Use converters to bind visual elements to ViewModel / Model properties
      ie: Model’s Temperature  Colour Brush
      Events are hooked up through either code-behind or commanding
      Commanding better, but no OOB support in SL
      Silverlight Extensions project on CodePlex
      Custom Behaviors
      Composite Application Guidance/Library (Prism)
      Design Patterns: MVVM
    • 12. View and ViewModel Binding
      ModelData md;
      public ViewModel()
      md=new ModelData();
      public string Data
      get{ return md.Data;}
      set{ md.Data = value;}
      public App() {
      View view = new View();
      view.DataContext= new ViewModel(); //…
      Content=“{Binding Data}” ... />
    • 13. Can use “regular” property procedures in ViewModel
      If binding a collection to a DataGrid, etc., prefer the ObservableCollection<> (or non-generic equivalent) to sync updates back to the Model automatically
      MVVM Data Binding
    • 14. MVVM Collection Item Binding
      The View should never bind to the data directly, but bind to a ViewModel
      If a collection of data is to be displayed in the View, the main ViewModel should expose an ObservableCollection of an additional ViewModel class that exposes properties, and thus, data
      Property ...
      Property ...
      Property ...
      Property ...
      Property ...
      Property ...
      public ObservableCollectionMyOC ...{
      return new ObservableCollection<ViewModel2> ...
      Property ...
      Property ...
      Property ...
      {Binding MyOC}” .../>
      Property ...
      Property ...
      Property ...
      Property ...
      Property ...
      Property ...
      The View
    • 15. Issue: changing property values in ViewModel does not always update bound control in View
      Solution: have ViewModel implement INotifyPropertyChanged interface, and raise PropertyChanged event in each property
      Or better yet, create a base ViewModel class and have each ViewModel subclass it
      Property Binding
    • 16. Attached Properties in XAML can also be used in lieu of missing Command
      Create Command, expose as property in ViewModel
      Create static class with Attached Property
      Add namespace to XAML screen
      Place Attached Property in desired control
      Commands and Attached Properties
    • 17. Attached Property
    • 18. ViewModel and XAML with Attached Property
    • 19. The View knows about the ViewModel, but the ViewModel does not know about the View
      ViewModel is assigned to the DataContext of the View (Silverlight XAML)
      In xaml.cs codebehind for page
      In App.xaml.cs
      In XAML via Resource
      Associating ViewModel with View
    • 20. Create ViewModel base class (implement INotifyPropertyChanged)
      Have all ViewModels subclass base
      Expose NO models to View directly
      Use Attached Properties as ‘workaround’ to lack of Commands in Silverlight controls
      Possibly Behaviors …
      Good practices …
    • 21. Development
      Silverlight 3
    • 22. Easy to get sloppy – name all controls/elements
      UI elements should have the same naming convention as your private class variables (that’s what they become)
      ie: <Button x:Name=“_submitButton” />
      Prefix every resource with a “namespace”
    • 23. Use new Data Annotations framework (.NET 3.5/4.0)
      • [Required]
      • 24. [Range(1,100)]
      • 25. [StringLength(15)]
      • 26. [RegularExpresion(“^M.*”)]
      • 27. [CustomValidation(typeof(MyValidator, “MyValidationMethod”))
      Can be applied at class or property level
      Data Annotations are your friend
    • 28. Import System.ComponentModel.DataAnnotations
      Annotate properties/methods
      Can specify custom validation method
      TIP: Use a convention pattern
      • Create an interface (ie: IValidatableValidate() method)
      • 29. Use a method name convention (use a constant)
      Data Annotations
    • 30. Pull common control appearance into styles
      Break app-wide resources into multiple files
      (by merging resource dictionaries into App.xaml)
      Styles and Resources
    • 37. Optimizations
      Silverlight 3
    • 38. Use Visibility rather than Opacity to hide objects
      Use transparent control backgrounds sparingly
      Avoid long-running JavaScript tasks and more
      Performance Tips …
    • 39. Never make the user wait and wonder
      Progress, progress, progress
      Minimize XAP size (this initial download)
      Make services prime, but remember
      Progress, progress, progress
      User interaction
    • 40. Resizing
      Drawing resultant pixels onscreen
      ALL can be done with GPU acceleration enabled
      In <object> tag
      <parm name=“enableGPUAcceleration” value=“true” />
      Hardware optimization
    • 41. Q&A
      Silverlight 3