Question

I’m looking to implement a chatroom interface for an ASP.NET page. I’m in the process of learning WCF and it seems that it is appropriate for a chat application. Before I get too involved into WCF I want to be sure it is the right choice to make for developing a chat application in ASP.NET. Can anyone provide any feedback?

I found a few example applications that primarily use Silverlight with WCF for chat applications. Are there any limitations if I choose not to use Silverlight?

Also, any alternatives to WCF that I would have full control over would be very helpful. I’m aware I can use AJAX polling, feedback on advantages/disadvantaged are all appreciated. Thank you.

Answer 1

You can use either Native ASP.Net approach or Silverlight approach to develop the good looking chat application.

The only concern is how your application is responsive to the end user. Here responsive means how the system let the user to feel the presense of other users and real time chat experience. This is refrenced sometime as really real time. (Like gmail & facebook webchat allows the user to see the user presense saying “user is typing or idle”)

You can achive this level of realtime appearance using both these technologies. But implementation are little different.

In order to achive this, you must implement a duplex communication between the browser and server. So then server will notify the client if there is any response from other user or his presense.

In ASP.Net way:

• This is been completely controlled by
  AJAX.
• You have to simulate the Duplex communication using AJAX. By default HTTP doesnt support duplex. Its oneway. It only responses to client request. It cant directly invoke client method .
• There are existing techniques available to achive this. One of the approach is called COMET or ReverseAJAX.
• Its nothing but the long living AJAX calls, and will respond to the client if there is a expected event happening in server side, otherwise it stays calm. This Comet (programming) wikipedia article explains more about the approach.

In SilverLight way:

• Silverlight gives much better User experience compared to normal HTML pages.
• By using SL, you can make use of WCF Duplex services to implement the server push technique. As per MSDN, it says

A duplex service contract is a message
exchange pattern in which both
endpoints can send messages to the
other independently. A duplex service,
therefore, can send messages back to
the client endpoint, providing
event-like behavior

• Here the nice example implementing duplex in SL.

Hope this helps