【翻译】WPF应用程序模块化开发快速入门（使用Prism+MEF）【下】

    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);

            // The boostrapper will create the Shell instance, so the App.xaml does not have a StartupUri.
            QuickStartBootstrapper bootstrapper = new QuickStartBootstrapper();
            bootstrapper.Run();
        }
    }

        protected override DependencyObject CreateShell()
        {
            return this.Container.GetExportedValue<Shell>();
        }

        protected override void InitializeShell()
        {
            base.InitializeShell();

            Application.Current.MainWindow = (Shell) this.Shell;
            Application.Current.MainWindow.Show();
        }

创建模块

在此快速入门示例中

创建了六个模块

这些模块都实现了IModule接口

添加了相关的特性

选择了依赖属性

    [ModuleExport(typeof(ModuleA), DependsOnModuleNames = new string[] { "ModuleD" })]
    public class ModuleA : IModule

当使用MEF框架的时候

ModuleExport特性允许MEF发现适当的、

继承自IModule接口的类型。

此外：它还支持详细说明额外模块的元数据

注册模块

在快速入门示例中

系统直接引用了一些模块

通过监控目录发现了一些模块

还有一些模块是通过配置文件加载的

QuickStartBootstrapper类型还重写了

CreateModuleCatalog和ConfigureModuleCatalog方法

这样就可以通过配置文件来注册模块

使用MEF时

AggregateCatalog支持发现模块和类型

基于此，

QuickStartBootstrapper重写ConfigureAggregateCatalog

模版方法并使用MEF注册程序集

仍然使用ModuleCatalog加载配置文件来注册模块

        protected override IModuleCatalog CreateModuleCatalog()
        {
            // When using MEF, the existing Prism ModuleCatalog is still the place to configure modules via configuration files.
            return new ConfigurationModuleCatalog();
        }

        protected override void ConfigureAggregateCatalog()
        {
            base.ConfigureAggregateCatalog();

            // Add this assembly to export ModuleTracker
            this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(QuickStartBootstrapper).Assembly));

            // Module A is referenced in in the project and directly in code.
            this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(ModuleA).Assembly));
            this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(ModuleC).Assembly));

            // Module B and Module D are copied to a directory as part of a post-build step.
            // These modules are not referenced in the project and are discovered by inspecting a directory.
            // Both projects have a post-build step to copy themselves into that directory.
            DirectoryCatalog catalog = new DirectoryCatalog("DirectoryModules");
            this.AggregateCatalog.Catalogs.Add(catalog);
        }

 在此快速入门中

即有在系统启动时加载模块的业务

也有按需加载模块的业务

还有显示进度、控制模块间的依赖性等业务

注意：

此快速入门示例还有一些额外的类

以帮助追踪模块初始化的状态信息

这些类主要是起了示范的目的

Shell的用户界面里包含了六个ModuleControl

Shell的DataContext是ModuleTracker

ModuleTracker类型为每个模块保存一个ModuleTrackingState

ModuleTrackingState绑定到与之对应的ModuleControl

ModuleControl使用一个默认的样式来展现模块的加载和初始化状态

当点击ModuleControl自定义控件的时候

将触发如下事件：

        /// <summary>
        /// Handles the RequestModuleLoad event of the ModuleC control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param>
        private void ModuleC_RequestModuleLoad(object sender, EventArgs e)
        {
            // The ModuleManager uses the Async Events Pattern.
            this.moduleManager.LoadModule(WellKnownModuleNames.ModuleC);
        }

此事件被触发的时候会同时触发moduleManager的ModuleDownloadProgressChanged事件

此事件是在shell页面的OnImportsSatisfied方法中被注册的

            this.moduleManager.LoadModuleCompleted += this.ModuleManager_LoadModuleCompleted;
            this.moduleManager.ModuleDownloadProgressChanged += this.ModuleManager_ModuleDownloadProgressChanged;

        /// <summary>
        /// Handles the LoadModuleProgressChanged event of the ModuleManager control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="Microsoft.Practices.Composite.Modularity.ModuleDownloadProgressChangedEventArgs"/> instance containing the event data.</param>
        private void ModuleManager_ModuleDownloadProgressChanged(object sender, ModuleDownloadProgressChangedEventArgs e)
        {
            this.moduleTracker.RecordModuleDownloading(e.ModuleInfo.ModuleName, e.BytesReceived, e.TotalBytesToReceive);
        }

        /// <summary>
        /// Handles the LoadModuleCompleted event of the ModuleManager control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="Microsoft.Practices.Composite.Modularity.LoadModuleCompletedEventArgs"/> instance containing the event data.</param>
        private void ModuleManager_LoadModuleCompleted(object sender, LoadModuleCompletedEventArgs e)
        {
            this.moduleTracker.RecordModuleLoaded(e.ModuleInfo.ModuleName);
        }

 关键类

（略）

这个系列含金量不高啊