Why is User (as in User.Identity.Name) null in my abstract base controller?

Question

I was asking a related question but messed the title up and no-one would understand it. Since I am able now to ask the question more precisely, I decided to reformulate it in a new question and close the old one. Sorry for that.

So what I want to do is passing data (my custom user's nickname as stored in the db) to the LoginUserControl. This login gets rendered from the master page via Html.RenderPartial(), so what I really need to do is making sure that, say ViewData["UserNickname"] is present on every call. But I don't want to populate ViewData["UserNickname"] in each and every action of every controller, so I decided to use this approach and create an abstract base controller which will do the work for me, like so:

public abstract class ApplicationController : Controller
    {
        private IUserRepository _repUser;

        public ApplicationController()
        {
            _repUser = RepositoryFactory.getUserRepository();
            var loggedInUser = _repUser.FindById(User.Identity.Name); //Problem!
            ViewData["LoggedInUser"] = loggedInUser;
        }
    }

This way, whatever my deriving Controller does, the user information will already be present.

So far, so good. Now for the problem:

I can't call User.Identity.Name because User is already null. This is not the case in all of my deriving controllers, so this is specific for the abstract base controller.

I am setting the User.Identity.Name via FormsAuthentication at another place in the code, but I think this can't be the problem - afaik User.Identity.Name can be null, but not User itself.

It looks to me like the HttpContext is not available (since also null ;-) and that I am missing a simple yet important point here. Can anyone give me some hints? I would really appreciate it.

Answer 1

The answer to this problem is actually quite simple. I can't execute the code from within the constructor for reasons pointed out by Raimond, but I can do it outside the constructor.

So what I did was overriding onActionExecuting() in the base controller class (I created a custom Attribute for it, but just overriding the method should also work) and then do my user lookup from there.

Now it works as expected and I have no repeated code.