Dynamic V Strongly Typed Views

There are three ways to pass information from a controller to a view in ASP.NET MVC 3:

1. As a strongly typed model object.
2. As a dynamic type (using @model dynamic)
3. Using the ViewBag

I’ve written a simple MVC 3  Top Blog application to compare and contrast dynamic and strongly typed views. The controller starts out with a simple list of blogs:

using System.Collections.Generic;
using System.Web.Mvc;

namespace Mvc3ViewDemo.Controllers {

    public class Blog {
        public string Name;
        public string URL;
    }

    public class HomeController : Controller {

        List<Blog> topBlogs = new List<Blog>
      { 
new Blog { Name = "ScottGu", URL = "http://weblogs.asp.net/scottgu/"},
new Blog { Name = "Jon Galloway", URL = "http://weblogs.asp.net/jgalloway"},
new Blog { Name = "Scott Hanselman", URL = "http://www.hanselman.com/blog/"}
      };

        public ActionResult IndexNotStonglyTyped() {
            return View(topBlogs);
        }

        public ActionResult StonglyTypedIndex() {
            return View(topBlogs);
        }

        public ActionResult IndexViewBag() {
            ViewBag.BestBlogs = topBlogs;
            return View();
        }
    }
}

Right-click in the IndexNotStonglyTyped() method and add a Razor view.

Make sure the Create a strongly-typed view box is not checked. The resulting view doesn’t contain much:

@{
    ViewBag.Title = "IndexNotStonglyTyped";
}

<h2>IndexNotStonglyTyped</h2>

On the first line of the Views\Home\IndexNotStonglyTyped.cshtml file, add the model directive and
the dynamic keyword.

@model dynamic

Because we’re using a dynamic and not a strongly typed view, intellisense doesn’t help us. The completed code is shown below:

@model dynamic
           
@{
    ViewBag.Title = "IndexNotStonglyTyped";
}

<h2>Index Not Stongly Typed</h2>

<p>
 <ul>
@foreach (var blog in Model) {
   <li>
    <a href="@blog.URL">@blog.Name</a>
   </li>   
}
 </ul>
</p>

Now we’ll add a strongly typed view. Add the following code to the controller:

public ActionResult StonglyTypedIndex() {
    return View(topBlogs);
}

Notice it’s exactly the same return View(topBlogs); call as the non-strongly typed view. Right click inside of StonglyTypedIndex() and select Add View. This time select the Blog Model class and select List as the Scaffold template.

Inside the new view template we get intellisense support and our view model is automatically scaffolded. Those are significant advantages and why ASP.NET MVC applications typically use strongly typed views. Strongly-typed view gives you:

• Automatic scaffolding
• Intellisense
• Compile time type checking (follow link to enable this)

Another non-strongly typed way we can pass the top blogs into a view template is to use the view bag.  ViewBag is new to MVC 3 and has the advantage that it can be used in combination with a strongly typed model, giving you the advantages for both. ViewBag is useful when you want to pass information not related to the view model and you don’t want to create a view model just to pass the information. For example, you can use it to pass information to your layout template. Be sure to read ScottGu’s post where he talks about ViewBag.

Add the following action method to the controller:

public ActionResult IndexViewBag() {
            ViewBag.BestBlogs = topBlogs;
            return View();
        }

The IndexViewBag.cshtml view template :

@{
    ViewBag.Title = "Index_ViewBag";
}

<h2>Index View Bag</h2>

<p>
 <ul>
@foreach (var blog in ViewBag.BestBlogs) {
   <li>
    <a href="@blog.URL">@blog.Name</a>
   </li>   
}
 </ul>
</p>

Good ViewBag links:

• ScottGu’s post on ViewBag
• ViewBag dynamic in ASP.NET MVC 3 – by Hanan
• ViewBag in ASP.NET MVC 3 by David Hayden

The c# project can be downloaded here.