In addition to some of our earlier coverage on .Net and Comet, it looks like there may be some Comet-like things happening in the .Net/Silverlight world based on Eugene Osovetsky’s recent article, Pushing Data to a Silverlight Application:

• An Instant Messaging / Chat application. When a user types a message into your Silverlight app, you use WCF to make, for example, a SendChatMessage() call. But what about receiving messages that others type back? Sure, you could call something like ReceiveChatMessage() continuously in a loop, and it could return null if there are no messages waiting. But this is a lot of work, not to mention the severe implications this would have for the performance of your app. Wouldn’t it be nice if it “just worked”?
• A Monitoring application. A lot of people are writing applications that monitor something that can be changed at any time on the server. Maybe it’s a stock ticker / charting app, or maybe it’s monitoring some physical sensor… Again, you could continuously poll the server to see if anything changed, but this is inefficient.

To solve problems like this, we are trying to ship a “duplex” feature in Silverlight 2 Beta2. (There is a very good chance that the feature will make it in, but of course no guarantees, and anything I say about the design is subject to change by the time we ship). I’ll first give you a quick overview and then the details:

Obviously it is fairly light on details, but from what is stated you can see roughly how the interface might work. It will be interesting to see if they build anything into the Silverlight plugin to give them an advantage over people with .Net APIs to their Comet servers.