CacheDependency Class
Assembly: System.Web (in system.web.dll)
If you add an item to the cache that is dependent on another object, such as a file or array of files, the dependent item is automatically removed from the cache when the object changes. For example, suppose you create a DataSet object based on data in an XML file. You can add the DataSet to the cache with a CacheDependency object that makes the DataSet dependent on the XML file. If the XML file changes, the DataSet is removed from the cache.
You can add items with dependencies to your application's cache with the Add and System.Web.Caching.Cache.Insert methods. You cannot use the Item property to add items to the cache with dependencies.
To set up a dependency, you create an instance of the CacheDependency class, specifying the files, keys, or directories on which the item is dependent, and then pass the dependency to the Add or System.Web.Caching.Cache.Insert method. The CacheDependency instance can represent a single file or directory, an array of files or directories, or an array of files or directories along with an array of cache keys (these represent other items stored in the Cache object).
The following code example demonstrates using the HasChanged property to determine whether a CacheDependency changed since the previous request for an item in the Cache. The dt value passed in the start parameter is set to DateTime.Now.
// Insert the cache item.
CacheDependency dep = new CacheDependency(fileName, dt);
cache.Insert("key", "value", dep);
// Check whether CacheDependency.HasChanged is true.
if (dep.get_HasChanged()) {
get_Response().Write("<p>The dependency has changed.");
}
else {
get_Response().Write("<p>The dependency has not changed.");
}
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System.Web.Caching.CacheDependency
System.Web.Caching.AggregateCacheDependency
System.Web.Caching.SqlCacheDependency
Reference
CacheDependency MembersSystem.Web.Caching Namespace
Cache
Insert