how to reference controller function from another controller - entity-framework

Question

Trying to learn ASP MVC coming from Linux/LAMP background (in other words I'm a newb) ...
For some reason I can't seem to use a function defined in a controller in another controller.
Here's the function in my MessagesController.cs file:
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
When I try to reference it:
using LemonadeTrader.Models;
using LemonadeTrader.Controllers; // added this to pull the Messages::getMesssagesById
...
ViewBag.messages = lemondb.Messages.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
I get something along the lines of lemondb.Messages does not contain a method called GetMesssagesById.
How do I reference it?

Answer 1

You shouldn't be linking controller methods like this, not to mention that controllers shouldn't be performing data access directly. I would recommend you externalizing this function into a separate class/repository which could be used by both controllers.
Example:
public class MessagesRepository
{
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
}
and then:
public class FooController: Controller
{
public ActionResult Index()
{
var db = new MessagesRepository()
ViewBag.messages = db.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
public class BarController: Controller
{
public ActionResult Index()
{
var db = new MessagesRepository()
ViewBag.messages = db.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
OK, that's the first step. This code could be improved by decoupling the controllers from the repository by introducing an abstraction for this repository:
public interface IMessagesRepository
{
List<Message> GetMessagesById(string username);
}
public class MessagesRepository: IMessagesRepository
{
public List<Message> GetMessagesById(string username)
{
return db.Messages.Where(p => p.user == username).ToList();
}
}
then you could use constructor injection for those controllers:
public class FooController: Controller
{
private readonly IMessagesRepository _repository;
public class FooController(IMessagesRepository repository)
{
_repository = repository;
}
public ActionResult Index()
{
ViewBag.messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
public class BarController: Controller
{
private readonly IMessagesRepository _repository;
public class BarController(IMessagesRepository repository)
{
_repository = repository;
}
public ActionResult Index()
{
ViewBag.messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString());
return View();
}
}
finally you would configure your DI framework to pass the corresponding implementation into those controllers.
I would also recommend you replacing this ViewBag with a strongly typed view model:
public class MyViewModel
{
public List<Message> Messages { get; set; }
}
and then:
public ActionResult Index()
{
var model = new MyViewModel
{
Messages = _repository.GetMessagesById(Membership.GetUser().ProviderUserKey.ToString())
};
return View(model);
}

Answer 2

Place GetMessageById (and all other methods needed for accessing messages) to separate class and use the class everywhere you need to get Message data.
MessageService service = new MessageService();
ViewBag.messages = service.GetMessagesById(...);