在Startup.cs ConfigureServices方法

Question

ASP.NET核心接入服務我需要訪問裏面Startup.cs ConfigureServices方法的服務，我這樣做：

services.AddScoped<ICustomService, CustomService>(); 

var sp = services.BuildServiceProvider(); 

var service = sp.GetService<ICustomService>(); // this is null 

然而var service上面總是空。

我做錯了什麼？

Answer 1

我有這樣的問題 - 我有一個單身'設置'服務，我想使用。我解決了它的真正創建一個，然後通過讓你指定一個「供應商」，而不是僅僅註冊類，並添加一個漂亮的大註釋解釋這個超載登記，準確的實例與DI：

var settingsService = new SettingsService(_hostingEnvironment); 

//Add a concrete settings service which is then registered as the de facto settings service for all time. 
//we need to do this as we want to use the settings in this method, and there isn't a satisfactory method to 
//pull it back out of the IServiceCollection here (we could build a provider, but then that's not the same provider 
//as would be build later... at least this way I have the exact class I'll be using. 
services.AddSingleton<ISettingsService, SettingsService>((p) => settingsService); 

.. 
.. 
.. 
var thing = settingsService.SomeSettingIWant(); 

如果你想要的不是單身，而是暫時的，那麼我想你可以在那裏爲它創建一個具體的類。我知道它可能有點像作弊，但它會正常工作...