MSDN Magazine - September 2008 - (Page 75)

is never directly instantiated in the code—instead it is loaded as a dependency in the WatchListPresentationModel constructor: public WatchListPresentationModel(IWatchListView view ) AddWatchView Injects WatchModule WatchListView In addition to the views, WatchModule also registers the WatchListService, which contains the list data and is used for adding new items. The specific views being registered are the watch list and the watch list toolbar. After registration, the region manager is used and both views that were just registered are added to the WatchRegion and ToolbarRegion. ToolbarRegion WatchRegion Main Region NewsRegion Injects Regions and RegionManager Figure 5 Injecting Modules into the App Modules by themselves are not that interesting unless they can render content to the UI. In the previous section, you saw that the Watch module uses a region to add its two views. Using a region removes the need for the module to have any specific reference to the UI or have any knowledge of how the views injected will be laid out and displayed. For an example of this, Figure 5 depicts the regions into which WatchModule injects. CAL includes a Region class that is basically a handle that wraps these locations. The Region class contains a Views property that is a read-only collection of the views to be displayed within the region. Views are added to the region by calling the region’s add method. The Views property actually contains a generic collection of objects; it is not limited to containing only UIElements. This collection implements INotifyPropertyCollectionChanged so that the UIElement associated with the region can bind to it and observe changes. You might be wondering why the Views collection is weakly typed rather than being of type UIElement. Thanks to the rich template support in WPF, you can actually add models directly to the region. That model can then have an associated DataTemplate defined for it that will define the rendering for the model. If the item added is a UIElement or a user control, then WPF will just render it as is. This means that if you have a region that is a tab of open orders, you can simply add the OrderModel or OrderPresentationModel to the region and then define a custom DataTemplate to control the display rather than having to create a custom OrderView user control. Regions can be registered in two ways. The first way is defined in XAML by annotating a UIElement with a RegionName attached property. For example, the XAML for defining the MainToolbarRegion is as follows: Note, however, that if using attached properties doesn’t work for you or you need to register additional regions dynamically, you can manually create an instance of the Region class or derived class and add it to RegionManager’s Regions collection. Notice in the XAML snippet that the MainToolbarRegion is an ItemsControl. CAL ships with three region adapters that are registered by the bootstrapper—ContentControlRegionAdapter, ItemsControlRegionAdapter, and SelectorRegionAdapter. Adapters are registered with a RegionAdapterMappings class. Adapters all inherit from RegionAdapterBase, which implements the IRegionAdapter interface. Figure 6 shows the implementation of ItemsControlRegionAdapter. How the adapter itself is implemented depends completely on the type of UIElement to which it is being adapted. In the case of ItemsControlRegionAdapter, the bulk of its implementation is in the Adapt method. The Adapt method accepts two parameters. The first parameter is an instance of the Region class itself that RegionManager creates. The second parameter is the UIElement that represents the region. The Adapt method performs the relevant plumbing to ensure that the region works with the element. In the case of an ItemsControl, the adapter automatically removes any child items from the ItemControl itself and then adds them to the region. The region’s Views collection is then bound to the ItemsSource of the control. The second method overridden is CreateRegion, which returns a Figure 6 ItemsControlRegionAdapter public class ItemsControlRegionAdapter : RegionAdapterBase { protected override void Adapt(IRegion region, ItemsControl regionTarget) { if (regionTarget.ItemsSource != null || (BindingOperations.GetBinding(regionTarget, ItemsControl.ItemsSourceProperty) != null)) throw new InvalidOperationException( Resources.ItemsControlHasItemsSourceException); if (regionTarget.Items.Count > 0) { foreach (object childItem in regionTarget.Items) { region.Add(childItem); } regionTarget.Items.Clear(); } regionTarget.ItemsSource = region.Views; Once a region has been defined via XAML, it will automatically be registered at run time with RegionManager, one of the composition services registered by the bootstrapper. RegionManager is essentially a Dictionary where the key is the name of the region and the value is an instance of the IRegion interface. The RegionManager attached property uses a RegionAdapter to create this instance. msdnmagazine.com } } protected override IRegion CreateRegion() { return new AllActiveRegion(); } September 2008 75 msdnmagazine.com

Table of Contents Feed for the Digital Edition of MSDN Magazine - September 2008

MSDN Magazine - September 2008 Contents Toolbox CLR Inside Out Data Points Advanced Basics Office Space Cutting Edge Hierarchy ID New Features for Microsoft SQL Server 2008 Prism Data Services Advanced WPF Test Run Security Briefs Foundations { End Bracket }

MSDN Magazine - September 2008

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