This article provides an introduction to ASP.NET caching.

For additional ASP.NET overviews, refer to the following Microsoft Knowledge Base article:

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The ASP.NET cache is a general-purpose cache facility for Web applications. It provides both a simple interface for caching and a more advanced interface that exposes expiration and change dependency services.

Caching is an extremely important technique for building high-performance, scalable server applications. Some items that are expensive to construct can be built once and then used for some amount of time before they are considered invalid. These items are stored in memory where they can be efficiently retrieved and used without incurring the cost of reconstructing them.

To learn more about ASP.NET caching features, refer to the following topic in the Microsoft .NET Framework Software Development Kit (SDK) documentation: ASP.NET includes three caching features:

•	Output Caching
•	Fragment Caching
•	Cache APIs

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Output Caching

Output caching allows you to store the results that a dynamic page generates. On subsequent requests, the cached output is used to satisfy the request rather than dynamically executing the page code. Output caching is also referred to as page caching.

The following sample illustrates how to cache the output of the page for 30 seconds:

Visual Basic .NET Sample

<%@ Page Language="VB" %>
<%@ OutputCache Duration="30" VaryByParam="*" %>
<script runat=server>
Public Sub Page_Load()
   Response.Write(DateTime.Now.ToString())
End Sub
</script>
				

Visual C# .NET Sample

<%@ Page Language="C#" %>
<%@ OutputCache Duration="30" VaryByParam="*" %>
<script runat=server>
public void Page_Load()
{
   Response.Write(DateTime.Now.ToString());
}
</script>
				

Visual J# .NET Sample

<%@ Page Language="VJ#" %>
<%@ OutputCache Duration="30" VaryByParam="*" %>

<script runat=server>
public void Page_Load()
{
	get_Response().Write(System.DateTime.get_Now().ToString());
}
</script>
				

For more information about output caching, refer to the following topic in the .NET Framework SDK documentation:

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Fragment Caching

Fragment caching is useful when you need to cache only a subset of a page. This is accomplished by caching the outputs of a user control. Navigation bars, headers, and footers are good candidates for fragment caching.

For more information about fragment caching, refer to the following topic in the .NET Framework SDK documentation:

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Cache APIs

Cache Application Programming Interfaces (APIs) allow you to programmatically store arbitrary objects to memory so that your application can save the time and resources that it takes to re-create them. Cache APIs allow you to expire items from the cache based on the following credentials:

•	Time
•	File dependencies
•	Cache key dependencies

For an overview of the cache APIs, refer to the following topic in the .NET Framework SDK documentation: ASP.NET enables you to easily add, retrieve, and remove items from the cache. For information about adding, retrieving, and removing items from the cache, refer to the following topics in the .NET Framework SDK documentation:

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