asp.net-core – 如何从控制器中解析ASP NET 5中的EF7当前数据库

使用.AddDbContext< ApplicationDbContext>();在依赖注入系统中注册ApplicationDbContext的方法(在ConfigureServices()方法中)导致它注册为Scoped依赖(或者换言之“每个请求”).因此,您只需要从依赖注入系统获取它.

>将dbContext作为构造函数方法的参数添加到您的类中(您将使用dbContext).然后你必须使用依赖注入系统来获得这个类,例如将它添加为控制器构造函数的参数.

public class HabitsController : Controller
{
    public HabitsController(HabitService habitService)
    {

    }
}

public class HabitService
{
    private GetHabitsContext _dbContext;

    public HabitService(GetHabitsContext dbContext)
    {
        _dbContext = dbContext;
    }
}

>但是如果你不想使用构造函数注入来获取上下文,你可以使用GetService()方法得到必要的依赖项(但是你需要在ServiceProvider实例中,在下面的示例中,我也可以通过构造函数注入) .

using Microsoft.Framework.DependencyInjection; // for beta 6 and below
using Microsoft.Extensions.DependencyInjection; // for beta 7 and above
public class HabitService
{
    private IServiceProvider _serviceProvider;

    public HabitService(IServiceProvider serviceProvider)
    {
        _serviceProvider = serviceProvider;
    }

    public GetHabit()
    {
         var dbcontext = _serviceProvider.GetService<ApplicationDbContext>();
    }
}

>在第一种方法中,我们也可以通过GetService()方法获取HabitService(而不是通过构造函数注入).

using Microsoft.Framework.DependencyInjection; // for beta 6 and below
using Microsoft.Extensions.DependencyInjection; // for beta 7 and above

public class HabitsController : Controller
{
    public HabitsController(IServiceProvider serviceProvider)
    {
       var habitService= serviceProvider.GetService<HabitService>();
    }
}

public class HabitService
{
    private GetHabitsContext _dbContext;

    public HabitService(GetHabitsContext dbContext)
    {
        _dbContext = dbContext;
    }
}

谢谢Tseng的评论：

I should be noted,that it’s a pretty bad practice to inject the container into your objects. The container should only be referenced from the composition root and certain type of factories (which are implemented on application level,and not in the domain/business layer)

dbContext in HabitsController and _dbContext in HabitService are different contexts!

我检查过,这是相同的背景.