Accessing a database object (and other important data) in the View

Question

I know it's a bad practice to use database in the view. However, I'm also passing the User object and I wonder how I can make it easy to use.

I love the way it works in Ruby On Rails. You just create an @instance_variable in before_filter and call it from the controllers and from the views.

You can't do this in ASP.NET MVC though. So I created a class with all the data I need to pass to the view (DataContext and User):

public class XData
{
    public DBDataContext DB { get; set; }
    public User User { get; set; }
}

In controller's Initialize method I get all the data:

public XData X;

protected override void Initialize(RequestContext requestContext)
{
    base.Initialize(requestContext);

    X = new XData();

    X.DB = ...;
    X.User = ....;
}

Works great: I can get the database object from the view like this:

<%= Model.X.DB.Users.First().Name %>

In order to pass the data to the view, I have to do the following:

    public ActionResult Foo()
    {
        return View(new FooModel
                        {
                            X = X,
                            HelloMessage = "Hello world!"
                        });
    }

The thing I don't like here is that I always have to write the X = X thing. How can I initialize that automatically?

Thanks

Answer 1

You could place X in ViewData and write an HtmlHelper extension method to access X or override the View method of the controller and add a little reflection logic that maps every instance property of the controller to properties with matching names of your model (I guess Automapper could help here...)

Answer 2

I think you'll need to start by making your view strongly typed:

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<Namespace.XData>" %>

and in your controller:

 public ActionResult Foo()
    {
        var X = new XData();
        X.User = ....;
        X.SomeProperty = ...;
        X.Message = "Hello world!";
        return View(X);
    }

which allows you to access the object in your view like so:

<%: Model.User.UserName %>
<%: Model.Message %>

Answer 3

I've seen a similar problem where a lot of controllers return a similar model with only a few customizations. In this case, create an abstract base model that other models derive from, and a function that returns the particular model you need with the base X = X and so forth already set.

For example, consider this:

public abstract class MyBaseModel
{
    public User User { get; set; }
}

public class FooModel : MyBaseModel
{
    public string FooMessage { get; set; }
}

public class BarModel : MyBaseModel
{
    public string BarMessage { get; set; }
}

public class MyController : Controller
{
    public ActionResult Foo()
    {
        var model = this.GetModel<FooModel>();

        // Set the properties on FooModel.
        model.FooMessage = "Hello world!"

        return View(model);
    }

    public ActionResult Bar()
    {
        var model = this.GetModel<BarModel>();

        // Set the properties on BarModel.
        model.BarMessage = "Hello world 2!"

        return View(model);
    }

    protected T GetModel<T>() where T : MyBaseModel, new()
    {
        T model = new T();

        // Set the properties on MyBaseModel.
        model.User = ...;

        return model;
    }
}

If you want to share MyBaseModel and GetModel among many controllers, extract it out to a ModelProvider or something similar that is supplied to each controller, ideally through dependency injection.