C# 4 and .NET 4

Themes ❘ 1207
applying Themes to Pages
You can apply a theme to a page in several ways, declaratively or programmatically. The simplest declarative
way to apply a theme is via the directive, using the Theme or StyleSheetTheme attribute:
or:
Here myTheme is the name defined for the theme.
Alternatively, you can specify a theme to use for all pages in a site, using an entry in the web.config file for
your web site:
Again, you can use Theme or StyleSheetTheme here. You can also be more specific by using
elements to override this setting for individual pages or directories, in the same way as this element was used
in the previous section for security information.
Programmatically, you can apply themes in the code-behind file for a page. There is only one place where
you are allowed to do this — in the Page_PreInit() event handler, which is triggered very early on in
the lifecycle of the page. In this event, you simply have to set the Page.Theme or Page.StyleSheetTheme
property to the name of the theme you want to apply, for example:
protected override void OnPreInit(EventArgs e)
{
Page.Theme = "myTheme";
}
Because you are using code to do this, you can dynamically apply a theme file from a selection of themes.
This technique is used in the “Themes in PCSDemoSite” section.
defining Themes
Themes are defined in yet another of the “special” directories in ASP.NET — in this case App_Themes. The
App_Themes directory can contain any number of subdirectories, one per theme, where the name of the
subdirectory defines the name of the theme.
Defining a theme involves putting the required files for the theme in the theme subdirectory. For CSS style
sheets, you don’t have to worry about the filename; the theme system simply looks for a file with a .css
extension. Similarly, .skin files can have any filename, although it is recommended that you use multiple
.skin files, one for each control type you want to skin, and each named after the control it skins.
Skin files contain server control definitions in exactly the same format as you would use in standard
ASP.NET pages. The difference is that the controls in skin files are never added to your page; they are
simply used to extract properties. A definition for a button skin, typically placed in a file called Button
.skin, might be as follows:
This skin is actually taken from the DefaultTheme theme in PCSDemoSite, and is responsible for the look
of the button on the Meeting Room Booker page you saw earlier in this chapter.
When you create a skin for a control type in this way you don’t use an ID property.
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