How should I call model class which is written in MVC? - asp.net-mvc

Question

Hi I have model class which is written in MVC.I am using Ef database first approach. In model class I have some queries which deals with database. I have following questions :
1) Is it right way to use database related queries in Model and call that in controller or view?
2)If yes where I should call this model? In Controller or in view ??
3)How I should call this model? Say for example I have class called class1.cs in model.How I should call this model?

Answer 1

Your model contains classes that define the different objects troughout your project. This includes properties with their basic information and methods to perform actions on this object.
1)
Do you really need queries? Why not use the Entity Framework to do it for you? Create the mapping for your domain classes (either trough annotations or fluent api) and use the DbContext to retrieve and save the data stored in your database
2)
Ideally people create repositories that are injected into your controllers (Dependency Injection). These repositories can for example contain something like GetPersonById(int id). Inside this method there would be two things:
Perform an action on the domain object
Save it to the DbContext
For example:
public void Subscribe(int userID, Show show) {
var user = GetUserByID(userID);
if (!user.IsSubscribedTo(show.ShowID)) {
user.Subscribe(show);
_dbContext.SaveChanges();
}
}
Controller -> Method call in repository -> Perform action on corresponding domain object -> Save changes to the database
If you need something that doesn't require an object mutation, it's even more simple:
public User GetUserByID(int id) {
return _dbContext.Users.FirstOrDefault(x => x.ID == id);
}
3)
Trough repositories (see above). Your DbContext will have a bunch of DbSets that contain objects that correspond with every data entry in your database. Trough repositories you can work with these objects and manipulate them. When you call the DbContext.SaveChanges() method, it will look at what has changed in these lists and commit the changes to your database.
Repository example:
class User {
public int ID { get; set; }
public string Name { get; set; }
}
class DatabaseContext : DbContext {
public DbSet<User> Users { get; set; }
}
public interface IUserRepository {
User GetUserByID (int id);
bool UsernameExists (string name);
}
public class UserRepository : IUserRepository {
private DatabaseContext _db;
public UserRepository(DatabaseContext db){
_db = db;
}
public User GetUserByID(int id) {
return _db.Users.FirstOrDefault(x => x.ID == id);
}
public User GetUserByUsername(string username) {
return _db.Users.FirstOrDefault(x => x.Name == username);
}
}
public class UserController : Controller {
private IUserRepository _userRepository;
public UserController(IUserRepository userRepository) {
_userRepository = userRepository;
}
public ActionResult Details(int id){
return View(_userRepository.GetUserByID(id);
}
}
// Ninject settings (install this extension, you want it):
private void AddBindings(){
kernel.Bind<DatabaseContext>().ToSelf().InSingletonScope();
kernel.Bind<IUserRepository>().To<UserRepository>().InRequestScope();
}

Answer 2

You could use some sort of Unit Of Work pattern which you inject in your controller constructor using an inversion of control container (IOC), for instance autofac.
Your unit of work class could hold a reference to repositories, where you would query/insert your data.
Roughly;
public class BackendController : Controller
{
private UnitOfWork _worker;
public BackendController(UnitOfWork worker)
{
this._worker = worker;
}
public ActionResult Admin()
{
var items = _worker.MyRepository.GetAll();
return View(items);
}
}
public class UnitOfWork
{
private ContentRepository _contentRepository;
public UnitOfWork()
{
}
public ContentRepository MyRepository
{
get
{
if (_contentRepository != null)
return _contentRepository;
else
return _contentRepository = new ContentRepository();
}
}
}
public class ContentRepository
{
// holds an object context and methods to retrieve and put data (EF or similar)
}
You would have to register your instance with the IOC container in global.asax, application_start for example, something like this (Using autofac as IOC):
UnitOfWork worker = new UnitOfWork();
var builder = new ContainerBuilder();
builder.RegisterControllers(Assembly.GetExecutingAssembly());
builder.RegisterInstance(worker).SingleInstance();
var container = builder.Build();
...

Answer 3

1) Is it right way to use database related queries in Model and call that in controller or view?
I would recommend not directly accessing the database in your model classes, as you have to remember that MVC is strictly a presentation layer pattern. If you do put your database access logic in your model classes, then you will not be able to have any other client use this functionality, such as a web service. Instead have logic that translates your business objects, defined outside of your ASP.NET MVC project, into your ASP.NET MVC model classes.
This is where the power of n-tier architecture shines, if you create a business and data-access layer, then I could write an ASP.NET MVC front-end, WebForms front-end, WPF front-end, WinForms front-end and all of them could access data using the same service. By putting the logic into the ASP.NET MVC model classes, then you are effectively forcing any other client to duplicate that logic again in their classes.