Any class that derives from the System.Web.Caching.CacheDependency class must implement this method.

When you derive from the System.Web.Caching.CacheDependency class, you use the base functionality of any method or property that you have not overridden. When you create an instance of the derived class, it represents the files, cache keys, database tables, or other arbitrary objects that you want to make a cached item dependent upon. When a dependency item changes, this method notifies the base functionality of the System.Web.Caching.CacheDependency class that the item has changed, so that the values of the CacheDependency.HasChanged and CacheDependency.UtcLastModified properties can be updated.