The objective of this article is to demonstrate how to use duck typed (dynamic) view models with ASP.NET MVC, especially when you work with fluid data stores like XML. As we are using .NET dynamic features, you’ll need VS2010 beta or RC to work with the samples. Full source code is available, but I’ll recommend you to go through the article before you download.
Alright, to start with, have a look at the application screen shot below. It is a simple Twitter search app in ASP.NET MVC, that can show you the latest tweets about what you search for.
Have a look at my controller. I just created an ASP.NET MVC 2 application in VS2010 and added references to Microsoft.CSharp.dll and AmazedSaint.Elastic project (included in the download above). AmazedSaint.Elastic namespace contains my ElasticObject implementation, I blogged about previously. Basically, ElasticObject can be used as a fluent dynamic wrapper to work with data formats like XML, and it is expected to evolve as smarter cousin of C# 4.0 ExpandoObject.
So, let us get back to the controller. VS already created the templates for me, and I modified the Index action in HomeController like this.
You might have noticed that I added a ‘query’ parameter to the Index action. Also, I’ve left out the event handler, so if your twitter connection is broken, the application will crash in your face :). We are parsing the atom format (it is xml) to an XElement, and then creating an ElasticObject out of that. If you are wondering what the heck is ToElastic() method, you should see this. Otherwise, if you can imagine, read on.
The view is also pretty minimal. Two interesting points here. Firstly, we are inheriting the page from ViewPage<dynamic>, which means the viewData we returned from controller gets passed here as a dynamic object. And everything else is pretty simple, isn’t it? We are just iterating through all elements with the name ‘entry’ in the Model (see the result of twitter api call http://search.twitter.com/search.atom?lang=en&q=aspnetmvc), to print the image, author name, tweet text etc.
According to ElasticObject conventions, ‘_All’ after an element name will return all elements with that name as shown above. Also, adding a tilde ‘~’ character before an element will return the content of that element. You don’t need that if the accessed item is an attribute (see how we are accessing the href). Again, have compare the elements we used in our view with the twitter api returned atom data if you still need clarity.
Hey, we are done. Run the app, and you can search tweets and view results. As you’ve noticed, we don’t have a strongly typed view model – We used ElasticObject to wrap the xml and passed it to the View. Yes, you need to read about ElasticObject – The source code of the above app and the source code of ElasticObject with few unit tests are available in the related download (see the link above). Minimal, happy coding with ASP.NET MVC, XML data and Duck typed view models. Finally, it is your choice, don’t kick me for using C# dynamic features :).