如何从应用程序的 MEF 容器中取消包含字段导入的对象的链接？

发布于 2024-10-13 03:25:59 字数 1595 浏览 3 评论 0原文

我正在编写一个在 .Net 4 中使用 MEF 的 WPF 应用程序。我的应用程序有一个 CompositionContainer，我的所有视图模型都可以访问该容器，以便访问（使用 MEF）一些负责数据检索和存储的共享对象。

我一直在使用内存分析器来查看视图模型对象和数据访问对象中的一些的生命周期，以查看何时对所有内容进行垃圾收集。令我惊讶的是，我发现我的应用程序的 CompositionContainer 在视图模型被释放后仍保留对它们的引用。

下面是我尝试大致展示我如何使用 MEF。我希望有人能告诉我我做错了什么。

App.xaml.cs 中的代码

公共部分类App：应用程序
{
    私有静态 CompositionContainer _container；
    内部静态 CompositionContainer Container { get { return _container; } }

    私有无效OnStartup（对象发送者，StartupEventArgs e）
    {
        AssemblyCatalog 目录 = new AssemblyCatalog(Assembly.GetExecutingAssembly());
        _container = new CompositionContainer(目录);
    }
}

合约接口

公共接口ICostCentreService：IBaseEntityService { ... }

实现接口的导出

[PartCreationPolicy(CreationPolicy.Shared)] [导出（类型（ICostCentreService））] 公共类 CostCentreService ：BaseEntityService、ICostCentreService { ... }

我的视图模型

公共类 CostCentreViewModel：ViewModelBase { [进口] 私有ICostCentreService _costCentreService;
 公共 CostCentreViewModel()
   {
       App.Container.ComposeParts(this);
   }
}

上面的代码能够提取足够多的图片来展示我如何使用 MEF。一旦我使用完视图模型并调用 Dispose 并删除对它的所有引用，就会出现问题，它不会被垃圾收集，因为应用程序的容器仍然引用它。（在我目前屏幕上的情况下，内存分析器表示我的视图模型仍然由 App._containner._partExportProvider._parts._items[0]._cashedIntance 引用）。

所以我想知道如何摆脱这个参考。是我没有正确使用 MEF 吗？

任何帮助将不胜感激。

干杯，

尼克·巴雷特

原文

I am writing a WPF application that uses MEF in .Net 4. My app has a CompositionContainer that is accessed by all my view models in order to get access to (using MEF) some shared objects that are responsible for data retrieval and storage.

I have been using a memory profiler to look at the lifetime of some of both my view model objects as well as the data access objects to see when everything is being garbage collected. To my surprise, I found that my app's CompositionContainer was keeping a reference to my view models after they had already been disposed.

The following is my attempt to show roughly how I'm using MEF. I'm hoping someone can show me how I'm doing it wrong.

Code in App.xaml.cs

public partial class App : Application
{
    private static CompositionContainer _container;
    internal static CompositionContainer Container { get { return _container; } }

    private void OnStartup(object sender, StartupEventArgs e)
    {
        AssemblyCatalog catalog = new  AssemblyCatalog(Assembly.GetExecutingAssembly());
        _container = new CompositionContainer(catalog);
    }
}

Contract interface

public interface ICostCentreService : IBaseEntityService
{
...
}

Exported class that implements interface

[PartCreationPolicy(CreationPolicy.Shared)]
[Export(typeof(ICostCentreService))]
public class CostCentreService : BaseEntityService, ICostCentreService
{
...
}

My view model class

public class CostCentreViewModel: ViewModelBase
{
[Import]
private ICostCentreService _costCentreService;
   public CostCentreViewModel()
   {
       App.Container.ComposeParts(this);
   }
}

Hopefully the code extracts above paint enough of a picture as to show how I am using MEF. The problem occurs once I have finished using the view model and I call Dispose and remove all references to it, it doesn't get garbage collected because the app's container still references it. (In the case I have on my screen at the moment, the memory profiler says my view model is still referenced by App._containner._partExportProvider._parts._items[0]._cashedIntance).

So I'm wondering how I get rid of this reference. Am I not using MEF properlly?

Any help would be much appreciated.

Cheers,

Nick Barrett

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