net core 3.1 依賴注入

Netcore內置IOC容器，services.AddSingleton<>,
就是往內置IOC容器里配置一個單例，將接口跟實現映射在一起，
以后每次使用構造函數注入這個IProductRepository接口，
都會獲得這個單例對象！ 不需要new ProductRepository()

DI --注入， IOC就是對象的容器， 配合起來就是依賴注入，按軟件設計原則來說，這叫控制反轉的作用

 

1.public interface HomeIBLL

2.public class HomeBLL : HomeIBLL
{
private readonly HomeIRepository _homeIRepository;
public HomeBLL(HomeIRepository homeIRepository)
{
_homeIRepository = homeIRepository;
}

3.public interface HomeIRepository

4.public class HomeRepository : HomeIRepository

5.services.AddSingleton<HomeIBLL, HomeBLL>();
services.AddSingleton<HomeIRepository, HomeRepository>();

6.private readonly HomeIBLL _homeIBLL;

public HomeController(ILogger<HomeController> logger, HomeIBLL homeIBLL)
{
_logger = logger;
_homeIBLL = homeIBLL;
}