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Caching Application Pages and Data FIGURE 29.10 Programmatically caching a User Control. LISTING 29.26 ShowDynamicUserControl.aspx void Page_Load() { // Load the control PartialCachingControl cacheMe = (PartialCachingControl)Page.LoadControl(“Movies.ascx”); // Change cache duration to 15 seconds cacheMe.CachePolicy.SetExpires(DateTime.Now.AddSeconds(15)); // Add control to page PlaceHolder1.Controls.Add(cacheMe); // Display control cache duration lblCacheDuration.Text = cacheMe.CachePolicy.Duration.ToString(); } . | 1374 CHAPTER 29 Caching Application Pages and Data FIGURE 29.10 Programmatically caching a User Control. LISTING 29.26 ShowDynamicUserControl.aspx @ Page Language C DOCTYPE html PUBLIC - W3C DTD XHTML 1.1 EN http www.w3.org TR xhtml11 DTD xhtml11.dtd script runat server void Page_Load Load the control PartialCachingControl cacheMe PartialCachingControl Page.LoadControl Movies.ascx Change cache duration to 15 seconds cacheMe.CachePolicy.SetExpires DateTime.Now.AddSeconds 15 Add control to page PlaceHolder1.Controls.Add cacheMe Display control cache duration lblCacheDuration.Text cacheMe.CachePolicy.Duration.ToString script From the Library of Wow eBook Using DataSource Caching 1375 html xmlns http www.w3.org 1999 xhtml head id Head1 runat server title Show Dynamic User Control title head body form id form1 runat server div Cache Duration asp Label id lblCacheDuration Runat server hr asp PlaceHolder id PlaceHolder1 Runat server div form body html In Listing 29.26 the default cache duration is modified by modifying the PartialCachingControl s CachePolicy property. This property returns an instance of the same ControlCachePolicy class described in the two previous sections of this chapter. You can refer to the User Control contained with an instance of the PartialCachingControl class by using the class s CachedControl property. Normally this property returns the value Nothing null because when the User Control is cached it is never actually created. Using DataSource Caching Instead of caching at the page or User Control level you can cache at the level of a DataSource control. Three of the four standard ASP.NET DataSource controls SqlDataSource ObjectDataSource and XmlDataSource include properties that enable you to cache the data that the DataSource control represents. The LinqDataSource control does not support caching. One advantage of using the DataSource controls when caching is that the DataSource controls can reload data automatically when the data is updated. .
