Ioc / DI - 为什么我必须引用入门程序中的所有图层/程序集？ [英] Ioc/DI - Why do I have to reference all layers/assemblies in entry application?
问题描述
（与此问题相关，。
但是，在松散耦合的应用程序中，通过将所有引用移动到组成根目录，依赖关系图被严重压平：
如绿色所示，现在可以重用库不要拖动任何不需要的依赖关系。
然而，所有这一切，与许多DI容器，你不有为所有必需的库添加硬引用。相反，您可以使用基于约定的汇编扫描（首选）或XML配置的形式的后期绑定。
当您执行但是，您必须记住将程序集复制到应用程序的bin文件夹，因为不再自动执行。就个人而言，我很少发现值得额外的努力。
(Related to this question, EF4 + MVC3: LazyLoading and ProxyCreation).
I'm new to DI so bear with me... I understand that the container is in charge of instantiating all of my registered types but in order to do so it requires a reference to all of the DLLs in my solution and their references.
If I wasn't using a DI container, I wouldn't have to reference EntityFramework library in my MVC3 app, only my business layer which would reference my DAL/Repo layer.
I know that at the end of the day all DLLs are included in the bin folder but my problem is having to reference it explicitly via "add reference" in VS in order to be able to publish a WAP with all necessary files...
If I wasn't using a DI container, I wouldn't have to reference EntityFramework library in my MVC3 app, only my business layer which would reference my DAL/Repo layer.
Yes, that's exactly the situation DI works so hard to avoid :)
With tightly coupled code, each library may only have a few references, but these again have other references, creating a deep graph of dependencies, like this:
Because the dependency graph is deep, it means that most libraries drag along a lot of other dependencies - e.g. in the diagram, Library C drags along Library H, Library E, Library J, Library M, Library K and Library N. This makes it harder to reuse each library independently from the rest - for example in unit testing.
However, in a loosely coupled application, by moving all the references to the Composition Root, the dependency graph is severely flattened:
As illustrated by the green color, it's now possible to reuse Library C without dragging along any unwanted dependencies.
However, all that said, with many DI Containers, you don't have to add hard references to all required libraries. Instead, you can use late binding either in the form of convention-based assembly-scanning (preferred) or XML configuration.
When you do that, however, you must remember to copy the assemblies to the application's bin folder, because that no longer happens automatically. Personally, I rarely find it worth that extra effort.
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