使用当前用户ID初始化ASP.NET MVC控制器

Question

I've created an ASP.NET MVC controller which responds with data from a data repository. The repository is pretty simple (underlying EF6 backend) and the data is specific to a user. So my actions typically look like this:

    public class MyController : Controller
    {
        private IRepository _repository = new MyDataContextRepository();

        [HttpPost]
        [Authorize]
        public ActionResult GetMyData()
        {
            var result = _repository.GetData(Membership.GetUser().ProviderUserKey);
            return Json(result);
        }
    }

But because I'll be using the user'd ID in nearly all the calls, I'd like to initialize the repository with the current user's ID instead, like so.

    public class MyController : Controller
    {
        private IRepository _repository = new MyDataContextRepository(Membership.GetUser().ProviderUserKey);

        [HttpPost]
        [Authorize]
        public ActionResult GetMyData()
        {
            var result = _repository.GetData();
            return Json(result);
        }
    }

The problem here is that the constructor is run before the user's officially logged in, so the GetUser() looks for the username "" (user not authorized yet).

Is it possible to initialize my data repository once after a user has been authenticated? Or can I only identify the user during the action method's call?

Answer 1

Standard practice would say that you should pass the user ID to the repository methods as a parameter, rather than basing the whole repository upon it.

But if you want to do it how you are, you can wrap the _repository in a property and create it the first time it is called. A simple way to do this is to use the Lazy<T> class. In this way the constructor will only be called the first time the repository is actually used and the User should be available then:

public class MyController : Controller
{
    private Lazy<IRepository> _repository = new Lazy<IRepository>(
        () => new MyDataContextRepository(Membership.GetUser().ProviderUserKey));

    private IRepository Repository
    {
        get { return _repository.Value; }
    }

    [HttpPost]
    [Authorize]
    public ActionResult GetMyData()
    {
        var result = Repository.GetData(); // the repository constructor will get called here
        return Json(result);
    }
}