16.1. Caching Pages

Problem

You want to cache the pages in your application.

Solution

Add the @ OutputCache directive to the top of the .aspx file of each page you want to cache with the VaryByParam attribute set to "None“:

	<%@ Page Language="VB" MasterPageFile="~/ASPNetCookbookVB.master"
         AutoEventWireup="false"
		 CodeFile="CH16CachePageVB.aspx.vb"
		 Inherits="ASPNetCookbook.VBExamples.CH16CachePageVB"
		 Title="Caching ASPX Pages" %>
    <%@ OutputCache Duration="5" VaryByParam="None" %>

           …

Discussion

This recipe shows the minimum changes required to an .aspx file to cache a page of your ASP.NET application. Only one @ OutputCache directive can be included per page, and the Duration and VaryByParam attributes are required.

You specify how long the page is to be retained in the cache by setting the Duration attribute to the desired time in seconds. In our example directive, the page will be rendered on the first request for the page and placed in the cache. For five seconds, all subsequent requests for the page will be delivered from the cached copy. After five seconds, the page will again be rendered.

The duration can be set to any positive integer value (1–2,147,483,647), which allows caching a page for roughly 68 years. You may be tempted to use very large numbers; however, every cached page uses server resources, and, if the page is not needed frequently, you will tie up server resources unnecessarily.

The VaryByParam attribute is used to define parameters that determine which cached copy ...

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