多个DbContext与单个DbContext - 数据库优先

Question

每次在同一个请求中调用存储库时，在内部实例化DbContext有什么好处？

我应该这样做：

public class HomeController : Controller
{

    public ActionResult Index()
    {
        var repo1 = new MyRepo1();
        var repo2 = new MyRepo2();
        var repo3 = new MyRepo3();

        return View();
    }
}

或者这个：

public class HomeController : Controller
{
    MyContext db = new MyContext();

    public ActionResult Index()
    {
        var repo1 = new MyRepo1(db);
        var repo2 = new MyRepo2(db);
        var repo3 = new MyRepo3(db);

        return View();
    }
}