Comet implementation for ASP.NET?

Actually there are many choices to create ajax supported website with ASP.NET but honestly, PokeIn is the easiest way to create an comet ajax supported web application. It has saved one of the projects of my company.

Comet is challenging to scale with IIS because of comet's persistent connectivity, but there is a team looking at Comet scenarios now. Also look at Aaron Lerch's blog as I believe he's done some early Comet work in ASP.NET.

WebSync is a standards-compliant scalable Comet server that integrates directly into the IIS/.NET pipeline. It's also available on demand as a hosted service.

It officially supports up to 20,000 concurrent client connections per server node, but individual tests have seen it go as high as 50,000. Message throughput is optimal around the 1,000-5,000 concurrent clients mark, with messages delivered as high as 300,000 per second from a single node.

It includes client-side support for JavaScript, .NET/Mono, iOS, Mac OS X, Java, Silverlight, Windows Phone, Windows Runtime, and .NET Compact, with server-side support for .NET/Mono and PHP.

Clustering is supported using either SQL Server or Azure Caching out of the box, but custom providers can be written for just about anything (Redis, NCache).

Disclaimer: I work for the company that develops this product.

I recently wrote a simple example of a Long Polling Chat Server using MVC 3 Async Controllers based on a great article by Clay Lenhart

You can use the example on a AppHarbor deployment I set up based on the source from the BitBucket project.

Also, more information available from my blog post explaining the project.