void InitializeStyleSheet ()
{
if (_styleSheetTheme == null) {
PagesSection ps = WebConfigurationManager.GetSection ("system.web/pages") as PagesSection;
if (ps != null)
_styleSheetTheme = ps.StyleSheetTheme;
}
if (!String.IsNullOrEmpty (_styleSheetTheme)) {
string virtualPath = "~/App_Themes/" + _styleSheetTheme;
_styleSheetPageTheme = BuildManager.CreateInstanceFromVirtualPath (virtualPath, typeof (PageTheme)) as PageTheme;
}
}