c# - .NET Core 3.1 框架提供 DI - 如何获取已注册类型的实例？

Question

在我的 .NET Core 3.1Startup.cs中，我试图获取已注册类型的实例，即IBusinessLogicusing IServiceCollection，但它不起作用。

如何在 .NET Core 3.1 中获取已注册类型的实例？

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {    
        container.Register<IBusinessLogic, BusinessLogic>();

        container.AddSingleton<Func<string, string>>
            ((username, password) => new JWTCache(userId, password, 
            container.GetInstance<IBusinessLogic>())); //container.GetInstance<IBusinessLogic>() not working
    }
}

Answer 1

您需要使用为您提供的重载IServiceProvider：

container.AddSingleton<Func<string, string>>(
    sp => (username, password) => new JWTCache(userId, password, sp.GetRequiredService<IBusinessLogic>())
);