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Change template programmatically

Describes how to programmatically change the template that is used to render a page.

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) {}
}