ASP.NET MVC 3 includes built-in JSON binding support that enables action methods to receive JSON-encoded data and model-bind it to action method parameters. 

To see this feature in action, consider the jQuery client-side JavaScript below.  It defines a “save” event handler that will be invoked when a save button is clicked on the client.  The code within the event handler constructs a client-side JavaScript “product” object with three fields whose values are retrieved from HTML input elements.  It then uses jQuery’s .ajax() method to POST a JSON based request containing the product to a /Store/UpdateProduct URL on the server:

ASP.NET MVC 3 now enables you to implement the /Store/UpdateProduct URL on the server using an action method like below:

The UpdateProduct() action method above accepts a strongly-typed Product object as a parameter.  ASP.NET MVC 3 can now automatically bind the incoming JSON post values to the .NET Product type on the server – without you having to write any custom binding or marshalling logic.  ASP.NET MVC’s built-in model and input validation features all work as you’d expect with this.

We think this capability will be particularly useful going forward with scenarios involving client templates and data binding (like I’ve previously blogged about here).  Client templates will enable you to format and display a single data item or set of data items by using templates that execute on the client.  ASP.NET MVC 3 will enable you to easily connect client templates with action methods on the server that return and receive JSON data.