问题描述
在 ASP.NET MVC 5 中，可以通过 DependencyResolver.Current.GetService 获得一些依赖关系.ASP.NET Core 中是否有类似的东西?
In ASP.NET MVC 5 is possible to obtain some dependency through DependencyResolver.Current.GetService<T>(). Is there something similar in ASP.NET Core?
推荐答案
是的，有.在 ASP.NET Core 1.0.0 中，来自 HttpContext 的请求中可用的服务通过 RequestServices 集合公开[1]:
Yes, there is. In ASP.NET Core 1.0.0, the services available within a request from HttpContext are exposed through the RequestServices collection[1]:
this.HttpContext.RequestServices
您可以使用GetService方法通过指定依赖的类型来检索依赖:
You can use the GetService method to retrieve the dependencies by specifying the type of the dependency:
this.HttpContext.RequestServices.GetService(typeof(ISomeService));
通常，您不应该直接使用这些属性，而是更愿意通过类的构造函数来请求您的类所需的类型，并让框架注入这些依赖项.这会产生更容易测试且耦合更松散的类.
Generally, you shouldn’t use these properties directly, preferring instead to request the types your classes you require via your class’s constructor, and letting the framework inject these dependencies. This yields classes that are easier to test and are more loosely coupled.
[1] https://docs.asp.net/en/latest/fundamentals/dependency-injection.html#request-services
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