Question

I’m trying to build a notifications provider (alerts) for my application. Currently I only need to generate notifications between requests, but having this functionality wrapped in a provider will allow me to hook it up to the database later.

I have 3 types of notifications:

public enum NotificationType
{
    Success,
    Error,
    Info
}

and a Notification object:

public class Notification
{
    public NotificationType Type { get; set; }
    public string Message { get; set; }
}

I would like to put all notifications in List<Notification> and load it into ViewData["Notifications"]

I could then use the helper to read ViewData["Notifications"] and render it:

I want to implement my own NotificationProvider which would maintain the List<Notification> object.

I want the provider to read TempData[“Notifications”] and load it into List<Notification> Notifications variable. I could then load notifications into ViewData[“Notifications”] for my helper to use.

Code below isn’t working but I think it shows what I’m trying to do.

public class NotificationProvider
{
    public List<Notification> Notifications { get; set; }

    private Controller _controller;

    public NotificationProvider(Controller controller /* How to pass controller instance? */)
    {
        _controller = controller;

        if (_controller.TempData["Notifications"] != null)
        {
            Notifications = (List<Notification>)controller.TempData["Notifications"];

            _controller.TempData["Notifications"] = null;
        }
    }

    public void ShowNotification(NotificationType notificationType, string message)
    {
        Notification notification = new Notification();

        notification.Type = notificationType;
        notification.Message = message;

        Notifications.Add(notification);

        _controller.TempData["Notifications"] = Notifications;
    }

    public void LoadNotifications()
    {
        _controller.ViewData["Notifications"] = Notifications;
    }
}

And in each controller a NotificationProvider instance:

public class HomeController
{
    private NotificationProvider notificationProvider;

    public HomeController()
    {
        notificationProvider = new NotificationProvider(/* Controller instance */);
        notificationProvider.LoadNotifications();
    }
}

Question:

How do I pass the controller instance to NotificationProvider class so it can access TempData and ViewData objects. Or if it’s possible, how can I access those objects directly from NotificationProvider instance?

Answer 1

I think you only want to pass this, like that. Also, back from comments, TempData will only be available in actions:

public class HomeController
{
    public ActionResult Index()
    {
        var notificationProvider = new NotificationProvider(this);
        notificationProvider.LoadNotifications();
        return View();
    }
}