Dispose DbContext in MVC Controller, which way "better"?

Question

In MVC 5, the scaffolding codes will have something like:

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

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            db.Dispose();
        }
        base.Dispose(disposing);
    }

otherwise, I need to have

using (var db = new MyContext())
{...}

in each action.

The codes look good, so I don't need to use using in each action. However, is this subject to preference of programmers, or such style has some advantage over using in each action that needs to use the dbcontext?

Answer 1

In terms of best practices, you should absolutely use the template scaffolded stuff and not mess with the using(){} pattern unless you have some really good overriding reason. Both solutions produce the same result, but both are not good solutions. The reason why the template has a single DbContext is to make it easier to test - heres an example:

public class SomeController : Controller
{
    private ApplicationDbContext db;

    public AccountController()
    {
        db = new ApplicationDbContext();
    }

    public AccountController(ApplicationDbContext context)
    {
        db = context;
    }
}

The first constructor with no arguments is that which is used in production and automatically creates a new db context based on the app config file. The second allows you to inject a mocked db context when you are doing unit testing.

At the end of the day, this question and my answer isn't really about disposing db contexts - it's about why the code template designers chose to take the approach they did and why it will help you. You should read more on unit testing.