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By the very nature of the Web and browsers, what you want to do isn't possible. There's no connection between the server and the client once a specific request has been satisfied. The server returns a response and forgets about the client. There's nothing you can do about that. This functionality is possible only for desktop apps. One workaround is to implement a background polling mechanism in the client-side by using JavaScript and the XmlHttpRequest object. With it, you can post a query to the server for information about changes. If you get new data in the response through the XmlHttpRequest, you can update the page view directly with DHTML from the JavaScript. This means the user will not see a page refresh.
On the server-side, you can either create an empty aspx form that processes these specific kind of posts, or you can create a custom IhttpHandler implementation, associate it with a new 'file' extension and process everything inside it. This is the most professional and reusable approach.
However, implementing this feature increases network traffic, so you have to evaluate its benefits carefully.
This was first published in June 2003