Change template programmatically

2 min

Given that there is a page model registered like:

[ContentType]
public class TypedPage: PageData {
  public virtual string Heading {
    get;
    set;
  }
  public virtual XhtmlString Content {
    get;
    set;
  }
}

You can have several templates defined for the same typed page. The following example registers two templates for the same typed page.

One is StandardTemplate without tags, which is the default template to use when rendering page instances of type TypedPage.

The other template is another generic template for pages more suitable for rendering mobile devices.

[TemplateDescriptor]
public partial class StandardTemplate : PageController<TypedPage> { }
    
[TemplateDescriptor(Name = "MobileTemplate")]
public partial class MobileTemplate : PageController<PageData> { }

To change the template used for a request, you can attach an event handler to an event raised when a template is chosen for a specific request. The following code sample attaches to the event and changes the template for a request for TypedPage instances when the request comes from a mobile device.

[InitializableModule]
public class MobileRedirectSample: IInitializableModule {
  private IHttpContextAccessor _httpContextAccessor;
  public void Initialize(InitializationEngine context) {
    _httpContextAccessor = context.Locate.Advanced.GetRequiredService<IHttpContextAccessor>();
    context.Locate.Advanced.GetRequiredService<ITemplateResolverEvents>().TemplateResolved += new EventHandler<TemplateResolverEventArgs>(MobileRedirectSample_TemplateResolved);
  }

  public void Uninitialize(InitializationEngine context) {
    context.Locate.Advanced.GetRequiredService<ITemplateResolverEvents>().TemplateResolved -= new EventHandler<TemplateResolverEventArgs> MobileRedirectSample_TemplateResolved);
}

void MobileRedirectSample_TemplateResolved(object sender, TemplateResolverEventArgs eventArgs) {
  if (eventArgs.ItemToRender != null && eventArgs.ItemToRender is TypedPage) {
    //The sample code uses package 'Wangkanai.Detection' for device detection
    var detection = _httpContextAccessor.HttpContext.RequestServices.GetRequiredService<IDetection>();
    if (detection.Device.Type == DeviceType.Mobile) {
      var mobileRender = eventArgs.SupportedTemplates
        .SingleOrDefault(r => r.Name.Contains("Mobile") &&
          r.TemplateTypeCategory == eventArgs.SelectedTemplate.TemplateTypeCategory);

      if (mobileRender != null) {
        eventArgs.SelectedTemplate = mobileRender;
      }
    }
  }
}

public void Preload(string[] parameters) {}
}