创建导入的 MEF 零件的多个实例

发布于 2024-07-22 05:52:18 字数 304 浏览 6 评论 0原文

目前，我的 WPF 应用程序导入了这样的部分，

[Import(typeof(ILedPanel)]
public ILedPanel Panel { get; set; }

但这为我提供了实现 ILedPanel 的类的单个实例。我真正想做的是能够创建尽可能多的实例我需要的。请注意，仅包含一项 ILedPanel 导出在任何给定时间使用该软件。

（如果我使用 List 的导入来给我一个实例对于每个实施 ILedPanel 的班级）

有什么建议吗？

原文

Currently my WPF application imports a part like this

[Import(typeof(ILedPanel)]
public ILedPanel Panel { get; set; }

But this gives ma a single intance of the class that implements ILedPanel.
What I really want to do is have the ability to create as many instances
that I need. Please note there is only one Export for ILedPanel included
with the software at any given time.

(If I use an import with List that gives me one instance
for every class implementing ILedPanel)

Any suggestions?

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撩起发的微风 2024-07-29 05:52:18

所有其他答案都相当旧，因此他们没有提到 MEF 中名为 ExportFactory。这个通用类允许您导入 ExportFactory 并在需要时创建任意数量的实例，因此您的代码将如下所示：

[Import(typeof(ILedPanel)]
public ExportFactory<ILedPanel> PanelFactory { get; set; }

public ILedPanel CreateNewLedPanelInstance()
{
    return PanelFactory.CreateExport().Value;
}

此方法还满足创建的部件具有的任何导入。您可以在此处了解有关使用 ExportFactory 类的更多信息。

All of the other answers are pretty old, so they don't mention a relatively new feature in MEF called ExportFactory. This generic class allows you to import ExportFactory<ILedPanel> and create as many instances as you like whenever you need them, so your code would look like this:

[Import(typeof(ILedPanel)]
public ExportFactory<ILedPanel> PanelFactory { get; set; }

public ILedPanel CreateNewLedPanelInstance()
{
    return PanelFactory.CreateExport().Value;
}

This method also satisfies any imports that created part has. You can read more about using the ExportFactory class here.

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囚你心 2024-07-29 05:52:18

我不确定这是否是尼古拉斯所指的，但您可以导入工厂类而不是实例类，如下所示：

[Import(typeof(ILedPanelFactory)]
public ILedPanelFactory PanelFactory { get; set; }

...然后在您的代码中...

ILedPanel panel = PanelFactory.BuildPanel();

I'm not sure if this is what Nicolas is referring to, but you could import a Factory class rather than an instance class, like this:

[Import(typeof(ILedPanelFactory)]
public ILedPanelFactory PanelFactory { get; set; }

...and then later in your code...

ILedPanel panel = PanelFactory.BuildPanel();

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忆梦 2024-07-29 05:52:18

今天 MEF 中没有对此的“内置”支持，但在恢复到服务定位器之前，您可能会在这里找到一些灵感：http://blogs.msdn.com/nblumhardt/archive/2008/12 /27/container-management-application-design-prelude-where-does-the-container-belong.aspx

基本思想是将容器“导入”到需要进行动态实例化的组件中。

我们正在探索对这种情况的更直接支持。

Nick

更新：MEF 现在对此提供了实验性支持。请参阅此博文了解更多信息。

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内心旳酸楚 2024-07-29 05:52:18

除非我误解了这个问题，否则看起来只需使用 CreationPolicy.NonShared 即可解决。

这假设声明面板的代码存在于您想要面板的任何地方。您将在具有此声明（导入）的每个类的每个实例中获得一个新的 ILedPanel 实例。

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柒夜笙歌凉 2024-07-29 05:52:18

查看 MEF 附带的形状游戏示例，有 ShapeFactory 类：

[Export]
public class ShapeFactory
{
    private readonly Random random = new Random((int)DateTime.Now.Ticks);

    [Import]
    private ICompositionService CompositionService { get; set; }

    public IShape GetRandomShape()
    {
        var shapeRetriever = new ShapeRetriever();

        CompositionService.SatisfyImports(shapeRetriever);

        int randomIndex = random.Next(shapeRetriever.PossibleShapes.Length);

        return shapeRetriever.PossibleShapes[randomIndex].GetExportedObject();
    }

    private class ShapeRetriever
    {
        [ImportMany(RequiredCreationPolicy = CreationPolicy.NonShared)]
        public Export<IShape, IShapeMetadata>[] PossibleShapes { get; set; }
    }
}

它演示了“按需”创建随机形状实例...我认为在您的场景中，您可以在不选择随机实现的情况下执行类似的操作，正如您所建议的，只有一种 ILedPanel 实现已注册。

Looking at the shapes game sample that comes with MEF, there is the ShapeFactory class:

[Export]
public class ShapeFactory
{
    private readonly Random random = new Random((int)DateTime.Now.Ticks);

    [Import]
    private ICompositionService CompositionService { get; set; }

    public IShape GetRandomShape()
    {
        var shapeRetriever = new ShapeRetriever();

        CompositionService.SatisfyImports(shapeRetriever);

        int randomIndex = random.Next(shapeRetriever.PossibleShapes.Length);

        return shapeRetriever.PossibleShapes[randomIndex].GetExportedObject();
    }

    private class ShapeRetriever
    {
        [ImportMany(RequiredCreationPolicy = CreationPolicy.NonShared)]
        public Export<IShape, IShapeMetadata>[] PossibleShapes { get; set; }
    }
}

Which demonstrates creating a random shape instances "on demand"... I would think in your scenario you could do something similar without the selection of a random implementation, as you suggest there would be only one implementation of ILedPanel registered.

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