building a customizable Web site complete with a collection of pluggable Web Parts is fairly easy with the portal infrastructure of ASP.NET 2.0. This model is very flexible, allowing users to easily place your Web Parts anywhere on the Web page so they are free to customize your site. However, these advantages can also lead to inefficiencies that may degrade the user experience, since you may not know beforehand which components will be used together, and therefore can’t make specific data retrieval optimizations for each individual component.
The most common inefficiency in a typical portal site occurs when multiple Web Parts simultaneously make network requests for data. Each request, whether to a Web service or a remote database, ends up adding to the overall time it takes to process the page even though the requests are typically independent of each other and could conceivably be issued in parallel.
Fortunately, ASP.NET 2.0 also introduces an easy-to-use asynchronous page model that, when used in combination with asynchronous Web service calls and asynchronous database access, can significantly improve the response time for a portal page as several independent Web Parts collect data in parallel. Here I’ll look at techniques for building Web Parts that perform their data retrieval asynchronously to make the portal pages that contain them more responsive and scalable.