用如下方法获取UserId报空引用异常

public class BaseController : Controller
{protected SiteContext db = new SiteContext();protected Guid userId;public BaseController(){userId = Guid.Parse(User.Identity.GetUserId());}
}

由于Controller未初始化完成，User为空，重写初始化方法，在初始化(base.Initialize(requestContext);)完成的时候再去获取User即可

解决方法：

public class BaseController : Controller
{protected SiteContext db = new SiteContext();protected Guid userId;protected override void Initialize(System.Web.Routing.RequestContext requestContext){base.Initialize(requestContext);if (User.Identity.IsAuthenticated){userId =Guid.Parse(User.Identity.GetUserId());}}
}