ASP.NET 2.0 Unleashed

The ASP.NET 2.0 Framework supports the following types of caching:

• Page Output Caching

• Partial Page Caching

• DataSource Caching

• Data Caching

Page Output Caching enables you to cache the entire rendered contents of a page in memory (everything that you see when you select View Source in your web browser). The next time that any user requests the same page, the page is retrieved from the cache.

Page Output Caching caches an entire page. In some situations, this might create problems. For example, if you want to display different banner advertisements randomly in a page, and you cache the entire page, then the same banner advertisement is displayed with each page request.

Note

The AdRotator control included in the ASP.NET Framework takes advantage of a feature called post-cache substitution to randomly display different advertisements even when a page is cached. Post-cache substitution is described later in this chapter.

Partial Page Caching enables you to get around this problem by enabling you to cache only particular regions of a page. By taking advantage of Partial Page Caching, you can apply different caching policies to different areas of a page.

You use DataSource Caching with the different ASP.NET DataSource controls such as the SqlDataSource and ObjectDataSource controls. When you enable caching with a DataSource control, the DataSource control caches the data that it represents.

Finally, Data Caching is the fundamental caching mechanism. Behind the scenes, all the other types of caching use Data Caching. You can use Data Caching to cache arbitrary objects in memory. For example, you can use Data Caching to cache a DataSet across multiple pages in a web application.

In the following sections, you learn how to use each of these different types of caching in detail.

Note

When configuring and debugging caching, having a tool that enables you to monitor the HTTP traffic between web server and browser is extremely helpful. You can download the free Fiddler tool, which enables you to view the raw request and response HTTP traffic, from http://www.FiddlerTool.com.