WICKED CODE: Supporting Database Cache Dependencies in ASP.NET

摘要

Developers love the ASP.NET application cache. One reason they love it is that ASP.NET lets them create dependencies between items placed in the cache and files in the file system. If a file targeted by a dependency changes, ASP.NET automatically removes dependent items from the cache. Combined with cache removal callbacks―notifications broadcast to interested parties when cached items are removed―cache dependencies are a boon to developers seeking to maximize performance by minimizing time-consuming file accesses because they permit file data to be cached without fear of it becoming stale. As awesome as cache dependencies are, in ASP.NET version 1.0 they lack one critical feature that, if present, would qualify them as a developers dream come true: support tor database entities. In real life, most Web apps fetch data from databases, not files. But while ASP.NET is perfectly willing to link cached items to files, it is incapable of linking cached items to database entities. In other words, you can read the contents of a file into a DataSet, cache the DataSet, and have the DataSet automatically removed from the cache if the file it was initial ized from changes. But you can't initialize a DataSet with a database query, cache the DataSet, and have the DataSet automatically discarded if the database changes. That's too bad because too many database accesses, like too much file I/O, is a performance killer.