使用来自另一个 MEF 程序集的类而不引用它 [英] Use classes from another MEF assembly without referencing to it

问题描述

我有 2 个 MEF 组件.让它成为组件 A 和组件 B.

I have 2 MEF components. Let it be component A and component B.

我需要的是能够从组件 A 中的组件 B 访问一个类而不引用它.然后我想手动实例化该类的对象.

What I need is to be able to access a class from component B in component A without referencing to it. Then I would like to instantiate object of the class manually.

目前我看到 MEF 允许使用 [Import] 自动实例化对象.它使用需要引用的接口.

Currently I see MEF allows instantiating an object automatically using [Import]. It uses interface which requires to be referenced to.

我可以使用来自其他程序集的数据类型而不引用它吗?MEF是否支持这种机制?

Can I use data types from another assemblies without referencing to it? Is there such mechanism supported by MEF?

推荐答案

有几种方法可以做到这一点.

There are a couple of ways to do this.

首先，您需要定义两个程序集都可以理解的通用接口.这可能是这两个程序集都引用的PublicInterfaces"库，或者它可能在程序集 A 内部(B 引用 A，但不是相反).

First, you need to define a common interface that both assemblies understand. This could be a "PublicInterfaces" library that both of these assemblies reference, or it could be inside of assembly A (B references A, but not the other way around).

在B中，使用该接口导出类型.

In B, export the type using this interface.

B 必须在容器的目录中.在 AssemblyCatalog 中显式引用程序集 B，或者创建一个 DirectoryCatalog 并将其指向将包含程序集 B 的目录.

B has to be in the container's catalog. Either reference assembly B explicitly in an AssemblyCatalog, or create a DirectoryCatalog and point it at the directory that will contain assembly B.

在 A 中，不使用 Import 属性，而是在容器上的代码调用 GetExportedValue<T>().代码如下所示:

In A, instead of using Import attributes, in code call GetExportedValue<T>() on the container. The code looks something like this:

// Known by A and B
public interface CommonInterface 
{
   // ...
}

// In B, not A
[Export(typeof(CommonInterface))]
public class BClass : CommonInterface
{
   // ...
}

// In A where you want to manually create class B
CommonInterface objB = _container.GetExportedValue<CommonInterface>();

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