MSDN Magazine - September 2008 - (Page 72)

also easily replaceable without recompilation of the created by the CreateShell method from within your Con gure the Container CAL. For example, the CAL ships with an extension application-specific bootstrapper. This is to ensure that uses the Unity Application Block for dependen- Con gure the Region Adapters that the bootstrapper’s initialization is completed cy injection but lets you replace this with your own before the shell is shown. dependency injection service. It may be surprising to know that you don’t actuCreate the Shell Quickstarts provide small, focused apps that demally need to have a shell in your application. For exonstrate using each of the different CAL components. ample, you may have an existing WPF application Load Modules They are designed to help you ramp up on concepts to which you want to add some CAL functionality. without having to grasp everything at once. Instead of having CAL control the entire screen, In the remainder of the article, I will explore several Figure 3 Bootstrapper you may want to add a panel that will be a top-level technical concepts of composites that are illustrated Initialization Tasks region. In this instance, you don’t need to define a in the Stock Trader reference implementation. All the code for the shell. Your bootstrapper can simply ignore displaying the shell if article is available in the Composite Application Guidance for WPF it is not defined. download from MSDN® at msdn.microsoft.com/library/cc707819. The Bootstrapper and Containers When you build composite applications using the CAL, you must first initialize several core composition services. This is where the bootstrapper comes in. It performs all the necessary functions for composition to occur (illustrated in Figure 3). In many ways it is the Main method of a CAL application. First, the container is initialized. By container I mean an inversion of control (IoC)/dependency injection (DI) container. If you are unfamiliar with this term, check out the MSDN Magazine article, “Tame Your Software Dependencies for More Flexible Apps,” by James Kovacs (msdn.microsoft.com/magazine/cc337885). Containers play a key role in a CAL app. The container is the store of all the app services used in composition. It is responsible for injecting theses services wherever they are needed. By default, the CAL includes an abstract UnityBootstrapper that uses the Unity framework from patterns & practices as the container. However, CAL was built to work with other containers such as Windsor, Structure Map, and Sprint.NET. None of the classes in the CAL (other than the Unity extensions) depend on a specific container. As the container is being configured, several core services used for composition are automatically registered, including a logger and an event aggregator, and the base bootstrapper lets you override any of these. For example, one service that is automatically registered is IModuleLoader. If you override the ConfigureContainer method in the bootstrapper, you can register your own module loader. protected override void ConfigureContainer() { Container.RegisterType (); base.ConfigureContainer(); } Finally, modules are initialized. A module in a CAL application is a unit of separation within a composite that can be deployed as a separate assembly, though this is not a requirement. In a CAL app, the module is what contains most of the functionality. Loading modules is a two-step process that involves two services: IModuleEnumerator and IModuleLoader. The enumerator is responsible for locating available modules. It returns several collections of ModuleInfo objects that contain metadata about a module. UnityBootstrapper contains a GetModuleEnumerator that should be overridden to return the correct enumerator; otherwise, an exception will be thrown at run time. The CAL includes enumerators for locating modules statically, from a directory scan, and from configuration. For loading, the CAL includes a ModuleLoader that is used by UnityBootstrapper by default. It loads each of the module assemblies (if they have not been loaded) and then initializes them. Modules can specify dependencies on other modules. The ModuleLoader will build a dependency tree and initialize modules in the correct order based on these specifications. Module Initialization Using the Bootstrapper If you don’t want services to be registered by default, you can turn that off also. Simply call the Run method overload on the bootstrapper, passing a false value for the useDefaultConfiguration parameter. Next, region adapters are configured. A region is a named location (usually a container, such as a panel) in the UI where modules can inject UIElements. Region adapters handle wiring different region types to be accessed. These adapters are mapped in a RegionAdapterMappings singleton instance in the container. At this point the shell is created. The shell is the top-level window where regions are defined. Instead of declaring it in App.Xaml, it is 72 msdn magazine Because UnityBootstrapper is an abstract class, StockTraderRIBootstrapper overrides it (see Figure 4). The bootstrapper has several protected virtual methods that allow you to insert your own application-specific functionality. The first thing you should notice is that an EntlibLoggerAdapter is defined and stored in the _logger variable. The code then overrides the LoggerFacade property to return this logger, which implements ILoggerFacade. In this case I am using the Enterprise Library’s logger, but you can easily replace this to use your own adapter. Next, the GetModuleEnumerator method is overridden to return a StaticModuleEnumerator that is pre-populated with the four reference implementation modules. The reference implementation uses static module loading, but there are several other ways to enumerate modules including directory lookup and configuration. To use a different method of enumeration, simply change this method to instantiate a different enumerator. ConfigureContainer is then overridden to register the shell. Additional services can also be programmatically registered at this point Composite WPF http://msdn.microsoft.com/library/cc707819 http://msdn.microsoft.com/magazine/cc337885

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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