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View models and partial views

This topic introduces the concept of views, view models and partial views, and provides some examples of how to use these when developing Optimizely CMS websites using ASP.NET Core.

How it works

In CMS, a template can correspond to a MVC controller and a view, where the controller selects the view to display. The view contains the actual HTML template with embedded code, generating content sent to the client. Another alternative is to use Razor pages as templates.

Views are .cshtml files stored by default in theViews folder. Action-specific views, partial views, and layouts are used to reduce repetition. By convention in MVC, the default layout is named _Layout.cshtmllocated in the Views/Shared folder. See Views (Microsoft).

To avoid repetition, you can create a base controller to be used by the page base class and inherited by other controllers. You can also create view models and partial views to make your views more flexible, for example, when creating menus and other navigation components.

View models

There are several ways of passing data to views. A view model is useful if you want to pass data beyond IContentData objects into your views. You can define a model type in the view, and pass an instance of this type to the view from the action.

In the following example, you use an interface IPageViewModel and a DefaultPageViewModel based on a SitePageData base class.

Example: Controller for a Standard page based on a PageController, using a DefaultPageViewModel.

namespace MyEPiServerSite.Controllers
    {
      public class StandardPageController : PageController<StandardPage>
      {
        public ActionResult Index(StandardPage currentPage)
        {
          /* Implementation of action. You can create your own view model class that 
             you pass to the view or you can pass the page type for simpler templates */
    
          DefaultPageViewModel<StandardPage> model = new DefaultPageViewModel<StandardPage>(currentPage);
          return View(model);
        }
      }
    }

Example: The DefaultPageViewModel with the IPageViewModel interface, and a ContentExtensions class used for rendering a left navigation section.

namespace MyOptimizelySite.Models.ViewModels
    {
      public class DefaultPageViewModel<T> : IPageViewModel<T> where T : PageData
      {
        public DefaultPageViewModel(T currentPage)
        {
          CurrentPage = currentPage;
          Section = ContentExtensions.GetSection(currentPage.ContentLink);
        }
        public T CurrentPage { get; set; }
        public IContent Section { get; set; }
      }
    }

PropertyFor is one of many Optimizely Html helpers. PropertyFor is frequently used for displaying markup for properties, and automatically enables on-page editing of the property when used.

Example: View for the Standard page, displaying the left navigation, with page name and main body properties.

@using MyEPiServerSite.Models.Pages
    @model MyEPiServerSite.Models.ViewModels.DefaultPageViewModel<StandardPage>
    
    @{
        Layout = "~/Views/Shared/Layouts/_LeftNavigation.cshtml";
    }
    
    <h1>
      @Html.PropertyFor(x => x.CurrentPage.PageName)
    </h1>
    <div class="row">
      <div class="span8 clearfix" >
        @Html.PropertyFor(x => x.CurrentPage.MainBody)
      </div>
    </div>

Partial views

A partial view is a view that is rendered within another view. The HTML output generated is rendered into the calling view. Common layout elements are usually defined in one view, and specific non-reusable layout elements are defined using partial views. See Partial views (Microsoft) for more information.

Example: A partial view for rendering a simple top navigation listing subpages to the start page, with links to each page.

@using EPiServer
    @inject IContentLoader ContentLoader
    @{
        var childPages = ContentLoader.GetChildren<PageData>(ContentReference.StartPage);
    }
    
    <b>@Html.ContentLink(ContentReference.StartPage)</b>
    @foreach (var page in childPages)
    {
      <b>
        @Html.ContentLink(page)
      </b>
    }

Example: The Navigation partial view added to the shared _Layout view, resulting in a top menu display for all pages.

@using EPiServer.Framework.Web.Mvc.Html
    @using EPiServer.Core
    
    @model IPageViewModel<SitePageData>
    
    <!DOCTYPE html>
    
    <html>
    <head>
      <title>@Model.CurrentPage.Name</title>
      <link rel="stylesheet" href="some.css" />
    </head>
    <body>
      @await Html.RenderEPiServerQuickNavigatorAsync()
    
      @Html.FullRefreshPropertiesMetaData()
      <div class="container">
        <div class="row">
          <div id="header">
            <div class="span2">
              <img src="/Static/gfx/logotype.png" />
            </div>
            <div class="span10">
              @{ await Html.RenderPartialAsync("Navigation"); }
            </div>
          </div>
        </div>
        <hr />
        @RenderBody()
      </div>
    </body>
    </html>

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