Using Output Cache

Using Output Cache

 

Output page caching is an ASP.NET feature that increases the performance of your web application by caching the HTML content generated from dynamic pages or controls. In other words, a page or user control that has output caching enabled is only executed the first time it is requested. On subsequent requests, the page or control is served directly from the cache, instead of being executed again.

 

The drawback with output caching is that if the information in the database changes in the meanwhile, your page will display outdated information. Also, enabling output caching, although it saves server-processing power, consumes server memory, and should be used with caution.

 

You can enable output page caching for a Web Form or Web User Control using the OutputCache page directive, which has a number of optional parameters:

<%@ OutputCache

Duration="#ofseconds"

Location="Any | Client | Downstream | Server | None"

Shared="True | False"

VaryByControl="controlname"

VaryByCustom="browser | customstring"

VaryByHeader="headers"

VaryByParam="parametername" %>

 

Explanation:

Shared: Applies only to user controls, and specifies whether the output of the user

control should be cached once for all the pages that include the control, or if multiple

versions of the control should be cached for each page that contains it.

 

VaryByParam: Varies the output cache based on the values of the parameters passed to

the server, which include the query string parameters.

 

For example:

<%@ OutputCache Duration="1000"

VaryByParam="DepartmentIndex;CategoryIndex;Search;AllWords;PageNumber;

ProductsOnPage" %>

 

Although implementing output page caching saves the database, it occupies web server memory.

 

For this reason, I recommend that implementing output caching for some static web user controls, such as Page Header, Page Footer, and so on.

 

Note: The above content is excerpted from ASP.NET 2.0 ecommerce in C# 2005 From Novice to Professional – Apress.