Data Caching
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:
DataSourceControlcachingSQL cache dependency
DataSourceControl Caching
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 ObjectDataSource, 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
Property | Type | Description | |||
|---|---|---|---|---|---|
| Integer | Length of time, in seconds, that data is cached before the cache is invalidated. Default value is | |||
|
| Default is | |||
| String | Creates a dependency between cache entries and a key. When the key expires, so does the cache. |