MEF和WPF無棱鏡

Question

有人可以告訴我一個在app.xaml.cs文件中構建MEF合成容器的示例，而無需使用棱鏡或控制台應用程序，這沒有問題。

導出有效，但導入無效，我看到的所有示例僅適用於我不想使用的Prism。 如果在App.xaml.cs文件中，導入將起作用，但是我不明白為什么在MainWindow.cs中導入將不起作用，並且一切都在根程序集中。

如果我在MainWindow構造函數中進行合成，則可以編寫它，但是如果可能的話，我想在app.xaml.cs中編寫。

這是一個示例（我實際上正在使用mvvm，但此示例的行為與后面的代碼相同）。

 public partial class App : Application
{
    public App()
    {
        ShutdownMode = ShutdownMode = ShutdownMode.OnMainWindowClose;

    }

    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);



        Compose();

       var window = new MainWindow();
        window.Show();

    }

    public void Compose()
    {
        var catalog = new AggregateCatalog(new AssemblyCatalog(Assembly.GetExecutingAssembly()), new DirectoryCatalog("."));
        var container = new CompositionContainer(catalog);
        container.ComposeParts(this);
    }


}

 [Export]
public class MessagePlugin
{
    public string GetMessage()
    {
        return "Successfully composed message";
    }

}

 public partial class MainWindow : Window
{
    [Import]
    public MessagePlugin plugin { get; set; }

    public MainWindow()
    {
        InitializeComponent();
        Loaded += MainWindow_Loaded;

    }


    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        var p = plugin; <-------------------------------NULL
        MessageBox.Show(p.GetMessage());

    }
}

Answer 1

public partial class App : Application
{
   private CompositionContainer container;

    [Import(typeof(Window))]
    public Window TheMainWindow { get; set; }


    public App()
    {
        ShutdownMode = ShutdownMode = ShutdownMode.OnMainWindowClose;
    }


    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        TheMainWindow = new MainWindow();

        Compose();

        Application.Current.MainWindow = TheMainWindow;
        Application.Current.MainWindow.Show();

    }

    public void Compose()
    {
        var catalog = new AggregateCatalog();
        catalog.Catalogs.Add(new AssemblyCatalog(typeof(App).Assembly));  
        container = new CompositionContainer(catalog);
        container.ComposeParts(this);
    }

}

[Export（typeof（Window））]公共部分類MainWindow：Window {[Import]公共MessagePlugin插件{get; 組; }

    public MainWindow()
    {
        InitializeComponent();
        Loaded += MainWindow_Loaded;

    }


    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        var p = plugin;

        if (p != null)
        {
            MessageBox.Show(p.GetMessage());
        }
        else
        {
            MessageBox.Show("Plugin NOT Composed");
        }


    }
}