When building a web application, it’s a common desire to want to expose a simple Web API along with the HTML user interface to enable various mash-up scenarios or to simply make accessing structured data easy from the same application.

A common question that comes up is when to use ASP.NET MVC to build out REST-ful services and when to use WCF? I’ve answered the question before, but not as well as Ayende does (when discussing a different topic). This is what I tried to express.

In many cases, the application itself is the only reason for development [of the service]

[of the service]” added by me. In other words, when the only reason for the service’s existence is to service the one application you’re currently building, it may make more sense  would stick with the simple case of using ASP.NET MVC. This is commonly the case when the only client to your JSON service is your web application’s Ajax code.

When your service is intended to serve multiple clients (not just your one application) or hit large scale usage, then moving to a real services layer such as WCF may be more appropriate.

However, there is now a third hybrid choice that blends ASP.NET and WCF. The WCF team saw that many developers building ASP.NET MVC apps are more comfortable with the ASP.NET MVC programming model, but still want to supply more rich RESTful services from their web applications. So the WCF team put together an SDK and samples for building REST services using ASP.NET MVC.

You can download the samples and SDK from ASP.NET MVC 1.0 page on CodePlex.

Do read through the overview document as it describes the changes you’ll need to make to an application to make use of this framework. Also, the zip file includes several sample movie applications which demonstrate various scenarios and compares them to the baseline of not using the REST approach.

At this point in time, this is a sample and SDK hosted on our CodePlex site, but many of the features are in consideration for a future release of ASP.NET MVC (no specifics yet).

This is where you come in. We are keenly interested in hearing feedback on this SDK. Is it important to you, is it not? Does it do what you need? Does it need improvement. Let us know what you think. Thanks!