CODEWITHSUNDEEP
asp.net-mvcdependency-injectionmockingunity-containereisk
user1582732
user1582732

Reputation: 59

Where does an MVC Controller get it's database context at run time

Given this code:

namespace Eisk.Controllers
{
    public class EmployeesController : Controller
    {
        DatabaseContext _dbContext;

        public EmployeesController(DatabaseContext databaseContext)
        {
            _dbContext = databaseContext;
        }

        public ViewResult Index()
        {
            var employees = _dbContext.EmployeeRepository;

            return View(employees.ToArray());
        }

Note that the constructor doesn't new up a database.

When accessed from a unit test I can inject a databaseContext and the controller will use that for the duration of the test. What I can't figure out is where this code is getting the database context it's using at run time. If I could find that out I might be able to figure out how to circumvent that behavior and have it use a mocked/in memory DB instead.

More explanation: I don't have access to a legacy database for this application right now so I'm trying to Mock up an in memory data source that gets filled from xml files. That's why I need to be able to circumvent the default database context creation.

More Information: Thanks for all the help so far you wonderful people you.

Steven seems to have directed me down the correct path. In the Global.asax file is this call:

DependencyInjectorInitializer.Init();

Following that through the code I get to:

        public static void Initialize()
    {
        _container = new UnityContainerFactory().CreateConfiguredContainer();     
        var serviceLocator = new UnityServiceLocator(_container);
        ServiceLocator.SetLocatorProvider(() => serviceLocator);
        DependencyResolver.SetResolver(new UnityDependencyResolver(_container));
    }

At least that gets me headed in the right direction. Now I have to figure out how Unity is going about creating the context so I can do my intervention.

Upvotes: 1

Views: 1194

Answers (1)

Steven
Steven

Reputation: 172676

With the default configuration of ASP.NET MVC, a controller should have a default constructor (i.e. a public constructor with no parameters). If not ASP.NET MVC will throw the following exception:

Type 'Eisk.Controllers.EmployeesController' does not have a default constructor

If this however works, this means that you (or another developer) overwrote the default configuration by either using a custom IControllerFactory or custom IDependencyResolver. Most developers do this by using an open source Dependency Injection library (such as Simple Injector, Autofac or Castle Windsor). If you pull in the NuGet MVC integration packages for such library, it will usually do this configuration for you. So somebody on your team might have done this for you.

My advice is: talk to your team and ask them how they did this and which container they used and where you can find the configuration for that.

Upvotes: 3

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