A newer version of this page is available. Switch to the current version.

How to: Use Custom Themes in ASP.NET Applications

  • 5 min to read

By default, an ASP.NET XAF application uses themes from the ASPxThemes Assembly. You can use custom assemblies as well. This topic details approaches to customizing default themes. To learn more about these themes, see the Appearance Customization - Theming topic in the ASP.NET controls documentation. To learn the basics behind the appearance of ASP.NET sites in XAF applications, refer to the ASP.NET Web Application Appearance topic.

This topic includes the following sections.

Add Assemblies with Custom Themes

You can add a custom theme in addition to the themes that are supplied with the DevExpress.Web.ASPxThemes.18.2.dll assembly. For this purpose, do the following.

  • Invoke ASP.NET Theme Builder as described in the Launching the Theme Builder topic, and create a new theme. For ASP.NET applications with the New Web UI, it is recommended to create themes based on the XafTheme theme. Customize the newly created theme and save changes.

    Note

    Ensure that the name of the newly created theme is unique for your project; otherwise change it in the Theme Properties... dialog.

    ThemeBuilder_ThemeProperties

    Currently, the Theme Builder tool does not support editing XAF-specific css files. So, it is necessary to modify css files manually.

  • After theme customization is finished, use Theme Builder to create an assembly with this theme. See the Generating a Custom Theme Assembly topic for details.
  • Reference this assembly in your web application project.
  • Open the application's Web.config configuration file, set the customThemeAssemblies attribute to the target assembly with a custom theme, and set themeName to the name of this theme in the theme element of the devExpress section.

    <devExpress>
        <!-- ... -->
        <themes enableThemesAssembly="true" customThemeAssemblies="ThemeAssembly1" theme="XafTheme1" />
    </devExpress>
    
  • Rebuild the solution.

See the Using a Custom Theme Assembly topic for additional information.

Override Skin Files from Built-in Themes

You can override skin files from themes located in a theme assembly. For this purpose, do the following.

  • Deploy skins from required themes to the App_Themes folder in your project. To do this, use the ASP.NET Theme Deployer tool.
  • Replace required skin files with custom ones.
  • Choose the default theme using the standard ASP.NET approach – by specifying the pages element in the application's Web.config configuration file.

    <configuration>
      <system.web>
        <pages theme="XafTheme1" />
        <!-- ... -->
      </system.web>
    <!-- ... -->
    </configuration>
    

    Leave the enableThemesAssembly attribute of the themes element set to true.

    <configuration>
      <devExpress>
        <!-- ... -->
        <themes enableThemesAssembly="true" />
      </devExpress>
    <!-- ... -->
    </configuration>
    

In applications with the Classic Web UI, themes, deployed to the App_Themes folder, will be added to the ChooseTheme Action as items, and will be available at runtime.

Override Built-in Themes

You can customize built-in themes. Follow the steps below to use them at runtime.

  • Deploy the required themes to the App_Themes folder in your project. To do this, use the ASP.NET Theme Deployer. They can be already customized, otherwise customize them directly in the project.
  • Set enableThemesAssembly to false and theme to an empty string in the themes element of the Web.config file.

    <configuration>
      <devExpress>
        <!-- ... -->
        <themes enableThemesAssembly="false"  theme=""/>
      </devExpress>
    <!-- ... -->
    </configuration>
    
  • Choose the default theme using the standard ASP.NET approach – by specifying the theme attribute of the pages element in the application's Web.config configuration file.

    <configuration>
      <system.web>
        <pages theme="XafTheme1" />
        <!-- ... -->
      </system.web>
    <!-- ... -->
    </configuration>
    

In applications with the Classic Web UI, themes, deployed to the App_Themes folder, will be added to the ChooseTheme Action as items, and will be available at runtime.

Register Additional CSS Files

If you need additional CSS files of a particular theme to be used on a page, register these files using the RegisterThemeAssemblyController. For this purpose, invoke the RegisterThemeAssemblyController's static RegisterCss method from a module's constructor. Pass the required style path as the method's path argument.

using DevExpress.ExpressApp.Web.SystemModule;
//...
public sealed partial class MyWebModule : ModuleBase {
    public MainDemoWebModule() {
        InitializeComponent();
        RegisterThemeAssemblyController.RegisterCss(
            "App_Themes/MyThemeAssembly/Xaf/MyExtraCustomStyles.css");
    }
}

Switch Between Themes for New and Classic Web UI

If you want to switch between themes for New and Classic Web UI according to the template chosen on the application start it is necessary to create a custom theme manager. The theme manager allows you to switch between themes depending on the device type or any other parameter. Note, that the standard ASP.NET way to set a theme in an application configuration file is not appropriate for this scenario.

Create an assembly with themes that use templates for the Classic and New web UI, as described in the Add Assemblies with Custom Themes section, and create a custom theme manager, which implements the ICurrentThemeManager interface. The code snippet below demonstrates an example of its implementation.

using DevExpress.ExpressApp.Web;
using DevExpress.ExpressApp.Web.Templates;
using DevExpress.ExpressApp.Utils;
//...
public class CustomThemeManager : ICurrentThemeManager {
    public string GetCurrentTheme() {
        if (WebApplicationStyleManager.IsNewStyle)
            return "NewStyleXafTheme";
        else
            return new SettingsStorageOnCookies().LoadOption("", "Theme");
    }
    public void SetCurrentTheme(string themeName) {
        new SettingsStorageOnCookies().SaveOption("", "Theme", themeName);
    }
}

Open the Global.asax.cs (Global.asax.vb) file, located in the application project, and add the following code to the Application_Start method to use the custom theme manager.

using DevExpress.ExpressApp.Web.SystemModule;
using DevExpress.ExpressApp.Web.Templates;
//...
public class Global : System.Web.HttpApplication {
    //...
    protected void Application_Start(Object sender, EventArgs e) {
        //...
        BaseXafPage.CurrentThemeManager = new CustomThemeManager();
    }
}