c# - PRISM + MEF -- 如何指定使用哪个导出？

Question

基本上，我如何指定要从哪些实现中进行选择？

FooService.cs:

public interface IFooService
{
    Int32 GetFoo();
}

[Export(typeof(IFooService))]
public sealed class Foo100 : IFooService
{
    public Int32 GetFoo()
    {
        return 100;
    }
}


[Export(typeof(IFooService))]
public sealed class Foo200 : IFooService
{
    public Int32 GetFoo()
    {
        return 200;
    }
}

ClientViewModel.cs:

[Export()]
public class ClientViewModel : NotificationObject
{
    [Import()]
    private IFooService FooSvc { get; set; }

    public Int32 FooNumber
    {
        get { return FooSvc.GetFoo(); }
    }
}

Boostrapper.cs:

public sealed class ClientBootstrapper : MefBootstrapper
{
    protected override void ConfigureAggregateCatalog()
    {
        base.ConfigureAggregateCatalog();

        //Add the executing assembly to the catalog.
        AggregateCatalog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));
    }

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

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

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

ClientShell.xaml.cs:

[Export()]
public partial class ClientShell : Window
{
    [Import()]
    public ClientViewModel ViewModel
    {
        get
        {
            return DataContext as ClientViewModel;
        }
        private set
        {
            DataContext = value;
        }
    }

    public ClientShell()
    {
        InitializeComponent();
    }
}

我不确定从这里去哪里设置我的应用程序以注入(inject)正确的应用程序(在这种情况下，我希望注入(inject) Foo100。我知道我可以让它们自己导出并指定一个 Foo100 IFooService，但这是正确的方法吗？

Answer 1

如果有多个导出与某个契约(Contract)，那么您将不得不全部导入它们(通过声明一个集合类型的属性并在其上添加 ImportMany 属性)或制定契约(Contract)通过指定契约(Contract)名称更具体:

[Export("Foo100", typeof(IFooService))]
public sealed class Foo100 : IFooService
{
    public Int32 GetFoo()
    {
        return 100;
    }
}


[Export("Foo200", typeof(IFooService))]
public sealed class Foo200 : IFooService
{
    public Int32 GetFoo()
    {
        return 200;
    }
}

-

[Import("Foo100", typeof(IFooService)]
private IFooService FooSvc { get; set; }