Implements the cache for a Web application. This class cannot be inherited.
Assembly: System.Web (in System.Web.dll)
The Cache type exposes the following members.
| Name | Description | |
|---|---|---|
.gif) | Count | Gets the number of items stored in the cache. |
| EffectivePercentagePhysicalMemoryLimit | Gets the percentage of physical memory that can be consumed by an application before ASP.NET starts removing items from the cache. |
| EffectivePrivateBytesLimit | Gets the number of bytes available for the cache. |
| Item | Gets or sets the cache item at the specified key. |
| Name | Description | |
|---|---|---|
.gif) | 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. |
| Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
.gif) | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
| Get | Retrieves the specified item from the Cache object. |
| GetEnumerator | Retrieves a dictionary enumerator used to iterate through the key settings and their values contained in the cache. |
| GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
| GetType | Gets the Type of the current instance. (Inherited from Object.) |
| 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. |
| Insert(String, Object, CacheDependency) | Inserts an object into the Cache that has file or key dependencies. |
| Insert(String, Object, CacheDependency, DateTime, TimeSpan) | Inserts an object into the Cache with dependencies and expiration policies. |
| 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. |
| 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. |
| MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
| Remove | Removes the specified item from the application's Cache object. |
| ToString | Returns a string that represents the current object. (Inherited from Object.) |
| Name | Description | |
|---|---|---|
.gif) | AsParallel | Enables parallelization of a query. (Defined by ParallelEnumerable.) |
| AsQueryable | Converts an IEnumerable to an IQueryable. (Defined by Queryable.) |
| Cast | Converts the elements of an IEnumerable to the specified type. (Defined by Enumerable.) |
| OfType | Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.) |
| Name | Description | |
|---|---|---|
.gif) .gif) | NoAbsoluteExpiration | Used in the absoluteExpiration parameter in an Insert method call to indicate the item should never expire. This field is read-only. |
| NoSlidingExpiration | Used as the slidingExpiration parameter in an Insert or Add method call to disable sliding expirations. This field is read-only. |
| Name | Description | |
|---|---|---|
.gif) .gif) | IEnumerable | Returns an enumerator that can iterate through the Cache object collection. |
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.
.gif) 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. |
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
<%@ Page Language="VB" %>
<html>
<Script runat=server>
Shared itemRemoved As boolean = false
Shared reason As CacheItemRemovedReason
Dim onRemove As CacheItemRemovedCallback
Public Sub RemovedCallback(k As String, v As Object, r As CacheItemRemovedReason)
itemRemoved = true
reason = r
End Sub
Public Sub AddItemToCache(sender As Object, e As EventArgs)
itemRemoved = false
onRemove = New CacheItemRemovedCallback(AddressOf Me.RemovedCallback)
If (IsNothing(Cache("Key1"))) Then
Cache.Add("Key1", "Value 1", Nothing, DateTime.Now.AddSeconds(60), Cache.NoSlidingExpiration, CacheItemPriority.High, onRemove)
End If
End Sub
Public Sub RemoveItemFromCache(sender As Object, e As EventArgs)
If (Not IsNothing(Cache("Key1"))) Then
Cache.Remove("Key1")
End If
End Sub
</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) Then
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(CType(Cache("Key1"),String)) + "</B>")
End If
%>
</body>
</html>
<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>
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.