TreeView in Razor Pages

This article describes how to seamlessly integrate and configure the Telerik UI Loader for ASP.NET Core in Razor Pages applications.

You can use any of the available data binding approaches to bind the component to data in a Razor Pages application.

Referencing Handler Methods in Razor Pages

Razor Pages is an alternative to the MVC pattern that makes page-focused coding easier and more productive. This approach consists of a cshtml file and a cshtml.cs file (by convention, the two files have the same name).

The cshtml.cs file, known as the PageModel, contains handler methods that respond to HTTP requests. These methods are prefixed with On followed by the HTTP verb (for example, OnGet, OnPost, OnPostRead, OnPostCreate).

Handler methods declared in a PageModel can be referenced from any Razor Page using one of the following URL patterns:

• Using Url.Page()

  C#

  Url.Page("PageName", "HandlerName")
  // OR
  Url.Page("/FolderName/PageName", "HandlerName")

  For example, Url.Page("Index", "Read") references the OnPostRead or OnGetRead handler method in the Index.cshtml.cs file.

• Using a query string

  C#

  Url("/PathToPage?handler=HandlerName")

  For example, Url("/Index?handler=Read") references the OnPostRead or OnGetRead handler method in the Index page.

For more information on Razor Pages architecture and concepts, refer to the official Microsoft documentation.

Binding to Remote Data

To configure the TreeView for remote data binding within a Razor Pages application, follow the next steps:

1. Define the TreeView and specify the Read request URL in the DataSource configuration. The URL must refer to the method name in the PageModel.

   HtmlHelperTagHelper

   Razor

   @page
   @model IndexModel
   @using Kendo.Mvc.UI
   
   @(Html.Kendo().TreeView()
       .Name("treeview")
       .DataTextField("Name")
       .DataSource(dataSource => dataSource
           .Custom()
           .Transport(t => t
               .Read(r => r.Url(Url.Page("Index", "TreeViewRead")).Data("forgeryToken").Type(HttpVerbs.Post)))
           )
   )

   Razor

   @page
   @model IndexModel
   @using Kendo.Mvc.UI
   
   <kendo-treeview name="treeview" datatextfield="Name" >
       <hierarchical-datasource type="DataSourceTagHelperType.Custom">
           <transport>
               <read url="@Url.Page("Index", "TreeViewRead")" type="post" data="forgeryToken" />
           </transport>
           <schema>
               <hierarchical-model id="ID" has-children="HasChildren">
               </hierarchical-model>
           </schema>
       </hierarchical-datasource>
   </kendo-treeview>

2. Add an AntiForgeryToken at the top of the page.

   Razor

       @inject Microsoft.AspNetCore.Antiforgery.IAntiforgery Xsrf
       @Html.AntiForgeryToken()

3. Send the AntiForgeryToken with the Read request.

   JavaScript

   <script>
       function forgeryToken() {
           return kendo.antiForgeryTokens();
       }
   </script>

   Additional parameters can also be supplied.

   JavaScript

   <script>
       function forgeryToken() {
           return {
               __RequestVerificationToken: kendo.antiForgeryTokens().__RequestVerificationToken,
               additionalParameter: "test"
           }
       }
   </script>

4. Within the cshtml.cs file, add a handler method for the Read data operation.

   Index.cshtml.csModel

   C#

       public static IList<HierarchicalViewModel> result = new List<HierarchicalViewModel>()
       {
           new HierarchicalViewModel() { ID = 1, ParentID = null, HasChildren = true, Name = "Parent Item 1" },
           new HierarchicalViewModel() { ID = 2, ParentID = null, HasChildren = true, Name = "Parent Item 2" },
           new HierarchicalViewModel() { ID = 3, ParentID = null, HasChildren = true, Name = "Parent Item 3" },
           new HierarchicalViewModel() { ID = 4, ParentID = 1, HasChildren = false, Name = "Child Item 1" },
           new HierarchicalViewModel() { ID = 5, ParentID = 1, HasChildren = false, Name = "Child Item 2" },
           new HierarchicalViewModel() { ID = 6, ParentID = 2, HasChildren = false, Name = "Child Item 3" },
           new HierarchicalViewModel() { ID = 7, ParentID = 2, HasChildren = false, Name = "Child Item 4" },
           new HierarchicalViewModel() { ID = 8, ParentID = 3, HasChildren = false, Name = "Child Item 5" },
           new HierarchicalViewModel() { ID = 9, ParentID = 3, HasChildren = false, Name = "Child Item 6" }
       };
   
       public void OnGet(string culture)
       {
           if (!String.IsNullOrEmpty(culture))
           {
               CultureInfo.DefaultThreadCurrentCulture = CultureInfo.DefaultThreadCurrentUICulture = new CultureInfo(culture);
           }
       }
   
       public JsonResult OnPostTreeViewRead(int? id)
       {
           var data = result.Where(x => id.HasValue ? x.ParentID == id : x.ParentID == null)
               .Select(item => new
               {
                   id = item.ID,
                   Name = item.Name,
                   hasChildren = item.HasChildren
               });
   
           return new JsonResult(data);
       }

   C#

   public class HierarchicalViewModel
   {
       public int ID { get; set; }
       public string Name { get; set; }
       public int? ParentID { get; set; }
       public bool HasChildren { get; set; }
   }

For the complete project, refer to the TreeView in Razor Pages example.

See Also

• Using Telerik UI for ASP.NET Core in Razor Pages
• Client-Side API of the TreeView
• Server-Side HtmlHelper API of the TreeView
• Server-Side TagHelper API of the TreeView
• Knowledge Base Section