www.gibmonks.com

Main Page

  Previous Section Next Section

Cache

System.Web.Caching (system.web.dll)sealed class

The Cache class allows your application to use data caching. The Cache class works by exposing a name/value collection where you can store objects that are expensive to create or frequently used. Its use is analogous to the System.Web.HttpApplicationState class, although you use the System.Web.HttpApplicationState to store information that must be retained for long periods of time and the Cache class for volatile objects that may quickly expire and can be dropped automatically when memory declines.

Much like the System.Web.HttpApplicationState class, the Cache class is globally accessible to all clients on a single web server, persists for the lifetime of the ASP.NET application, and has only one instance per application. Unlike the System.Web.HttpApplicationState class, the Cache class is intrinsically thread-safe.

You can add items to the cache as you would with other state collections like System.Web.HttpApplicationState (for example, Cache["myobject"] = dsData;). However, using the overloaded Insert( ) method allows much more control. For example, you can set an absolute expiration policy in which an item will be removed after a specified time (Cache.Insert("Data", dsData, null, DateTime.Now.AddMinutes(10), NoSlidingExpiration;) or a sliding expiration policy in which an item will be removed after a specified interval of disuse (Cache.Insert("Data", dsData, Nothing, NoAbsoluteExpiration, TimeSpan.FromMinutes(10);). Note that the NoAbsoluteExpiration and NoSlidingExpiration fields from the Cache class allow you to disable the type of caching you don't want to use. Attempts to retrieve a removed cached item will return Nothing (or null).

You can also use a version of the Insert( ) method with additional parameters for setting cache dependencies (by supplying an instance of a CacheDependency class), priorities (by using the CacheItemPriority enumeration), and a callback (by supplying a CacheItemRemovedCallback delegate).

The Cache class is available through the built-in Cache object and shouldn't be confused with the System.Web.HttpCachePolicy class, which is used to configure page caching and is available through the Response.Cache reference.

public sealed class Cache : IEnumerable {
// Public Constructors
   public Cache( );
// Public Static Fields
   public static readonly DateTime NoAbsoluteExpiration;         // =12/31/9999 11:59:59 PM
   public static readonly TimeSpan NoSlidingExpiration;          // =00:00:00
// Public Instance Properties
   public int Count{get; }
   public object this[string key]{set; get; }
// Public Instance Methods
   public object Add(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, 
        TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback);
   public object Get(string key);
   public IDictionaryEnumerator GetEnumerator( );
   public void Insert(string key, object value);
   public void Insert(string key, object value, CacheDependency dependencies);
   public void Insert(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, 
        TimeSpan slidingExpiration);
   public void Insert(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan
        slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback);
   public object Remove(string key);
}

Returned By

System.Web.HttpContext.Cache, System.Web.HttpRuntime.Cache, System.Web.UI.Page.Cache, System.Web.UI.UserControl.Cache

      Previous Section Next Section