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Cache Class

.NET Framework 4

Implements the cache for a Web application. This class cannot be inherited.

System.Object
  System.Web.Caching.Cache

Namespace:  System.Web.Caching
Assembly:  System.Web (in System.Web.dll)
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public sealed class Cache : IEnumerable

The Cache type exposes the following members.

  Name Description
Public method Cache Infrastructure. Initializes a new instance of the Cache class.
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  Name Description
Public property Count Gets the number of items stored in the cache.
Public property EffectivePercentagePhysicalMemoryLimit Gets the percentage of physical memory that can be consumed by an application before ASP.NET starts removing items from the cache.
Public property EffectivePrivateBytesLimit Gets the number of bytes available for the cache.
Public property Item Gets or sets the cache item at the specified key.
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  Name Description
Public method Add Adds the specified item to the Cache object with dependencies, expiration and priority policies, and a delegate you can use to notify your application when the inserted item is removed from the Cache.
Public method Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method Get Retrieves the specified item from the Cache object.
Public method GetEnumerator Retrieves a dictionary enumerator used to iterate through the key settings and their values contained in the cache.
Public method GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Public method Insert(String, Object) Inserts an item into the Cache object with a cache key to reference its location, using default values provided by the CacheItemPriority enumeration.
Public method Insert(String, Object, CacheDependency) Inserts an object into the Cache that has file or key dependencies.
Public method Insert(String, Object, CacheDependency, DateTime, TimeSpan) Inserts an object into the Cache with dependencies and expiration policies.
Public method Insert(String, Object, CacheDependency, DateTime, TimeSpan, CacheItemUpdateCallback) Inserts an object into the Cache object together with dependencies, expiration policies, and a delegate that you can use to notify the application before the item is removed from the cache.
Public method Insert(String, Object, CacheDependency, DateTime, TimeSpan, CacheItemPriority, CacheItemRemovedCallback) Inserts an object into the Cache object with dependencies, expiration and priority policies, and a delegate you can use to notify your application when the inserted item is removed from the Cache.
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method Remove Removes the specified item from the application's Cache object.
Public method ToString Returns a string that represents the current object. (Inherited from Object.)
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  Name Description
Public Extension Method AsParallel Enables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension Method AsQueryable Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension Method Cast(Of TResult) Converts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension Method OfType(Of TResult) Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
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  Name Description
Public field Static member NoAbsoluteExpiration Used in the absoluteExpiration parameter in an Insert method call to indicate the item should never expire. This field is read-only.
Public field Static member NoSlidingExpiration Used as the slidingExpiration parameter in an Insert or Add method call to disable sliding expirations. This field is read-only.
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  Name Description
Explicit interface implemetation Private method IEnumerable.GetEnumerator Returns an enumerator that can iterate through the Cache object collection.
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One instance of this class is created per application domain, and it remains valid as long as the application domain remains active. Information about an instance of this class is available through the Cache property of the HttpContext object or the Cache property of the Page object.

Note Note

The Cache class is not intended for use outside of ASP.NET applications. It was designed and tested for use in ASP.NET to provide caching for Web applications. For other types of applications, such as console applications or Windows Forms applications, use the ObjectCache class.
Topic Location
How to: Delete Items from the Cache in ASP.NET Building ASP .NET Web Applications
How to: Add Items to the Cache Building ASP .NET Web Applications
How to: Delete Items from the Cache in ASP.NET Building ASP .NET Web Applications
How to: Add Items to the Cache Building ASP .NET Web Applications

The following example is a page that shows users the value assigned to an item in the cache, and then notifies them when the item is removed from the cache. It creates a RemovedCallback method, which has the signature of the CacheItemRemovedCallback delegate, to notify users when the cache item is removed, and it uses the CacheItemRemovedReason enumeration to tell them why it was removed. In addition, it uses the Cache.Item property to add objects to the cache and retrieve the value of those objects. In the AddItemToCache method, it uses the Cache.Add method to add an item to the cache. To use the CacheItemRemovedCallback delegate, you must add an item to the cache with this method or the Cache.Insert method, so that that ASP.NET can automatically make the proper method calls when the item is removed. The custom RemoveItemFromCache method uses the Cache.Remove method to explicitly delete the item from the cache, causing the RemovedCallback method to be invoked.

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<html>
 <Script runat=server language="C#">
    static bool itemRemoved = false;
    static CacheItemRemovedReason reason;
    CacheItemRemovedCallback onRemove = null;

    public void RemovedCallback(String k, Object v, CacheItemRemovedReason r){
      itemRemoved = true;
      reason = r;
    }

    public void AddItemToCache(Object sender, EventArgs e) {
        itemRemoved = false;

        onRemove = new CacheItemRemovedCallback(this.RemovedCallback);

        if (Cache["Key1"] == null)
          Cache.Add("Key1", "Value 1", null, DateTime.Now.AddSeconds(60), Cache.NoSlidingExpiration, CacheItemPriority.High, onRemove);
    }

    public void RemoveItemFromCache(Object sender, EventArgs e) {
        if(Cache["Key1"] != null)
          Cache.Remove("Key1");
    }
 </Script>
 <body>
  <Form runat="server">
   <input type=submit OnServerClick="AddItemToCache" value="Add Item To Cache" runat="server"/>
   <input type=submit OnServerClick="RemoveItemFromCache" value="Remove Item From Cache" runat="server"/>
  </Form>
  <% if (itemRemoved) {
        Response.Write("RemovedCallback event raised.");
        Response.Write("<BR>");
        Response.Write("Reason: <B>" + reason.ToString() + "</B>");
     }
     else {
        Response.Write("Value of cache key: <B>" + Server.HtmlEncode(Cache["Key1"] as string) + "</B>");
     }
  %>
 </body>
</html>

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

This type is thread safe.

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  1.  Enter comment here.[<Sealed>]
    type Cache = 
        class
            interface IEnumerable
        end

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