Data caching is (surprise!) the caching of data from a data source. As long as the cache is not expired, a request for data will be fulfilled from the cache rather than the original data source. If the cache is expired for whatever reason, fresh data will be obtained by the data source and the cache will be refreshed. The cache can expire for many reasons, as you will see. These can include timeouts, changed data, or changes to other objects.
There are two kinds of data caching; both are very useful:
SQL cache dependency
As we showed in Chapters Chapter 7 through Chapter 10,
DataSource controls represent data in a data source, such as a database or an XML file. Of those that derive from the abstract
DataSourceControl class (see Figure 7-1 in Chapter 7), the
SqlDataSource, and its derived types have a number of read/write properties for implementing caching, as listed in Table 17-1.
Table 17-1. Data source control properties for caching
Length of time, in seconds, that data is cached before the cache is invalidated. Default value is
Creates a dependency between cache entries and a key. When the key expires, so does the cache.