DropDownTree in Razor Pages

Updated on Dec 10, 2025

This article describes how to seamlessly integrate and configure the Telerik UI DropDownTree 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

The most flexible form of data binding is to use the DataSource component. To bind the DropDownTree to a data set received from a remote endpoint within a Razor Pages application, follow the next steps:

1. Specify the Read request URL in the DataSource configuration. The URL must refer to the method name in the PageModel.

   Razor

       @page
       @model DropDownTreeIndexModel
   
       @(Html.Kendo().DropDownTree()		
           .Name("dropdowntree")
           .AutoWidth(true)
           .DataTextField("Name")
           .HtmlAttributes(new { style = "width: 100%" })
           .CheckAll(true)
           .AutoClose(false)
           .Checkboxes(checkboxes => checkboxes
               .CheckChildren(true)
           )
           .DataSource(dataSource => dataSource
               .Custom()
               .Transport(t => t
                   .Read(r => r.Url(Url.Page("DropDownTreeIndex", "DropDownTreeRead")).Data("forgeryToken")))
               )
       )

   Razor

       @page
       @model DropDownTreeIndexModel
   
       <kendo-dropdowntree name="dropdowntree" style="width: 100%"
           datatextfield="Name" 
           auto-close="false"
           auto-width="true">
           <hierarchical-datasource>
               <schema>
                   <hierarchical-model id="id"></hierarchical-model>
               </schema>
               <transport>
                   <read url="@Url.Page("DropDownTreeIndex", "DropDownTreeRead")" data="forgeryToken" />
               </transport>
           </hierarchical-datasource>
           <checkboxes check-children="true" enabled="true" />
       </kendo-dropdowntree>

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 operation that returns the dataset.

   C#

   public class DropDownTreeIndexModel : PageModel
   {
       public JsonResult OnGetDropDownTreeRead(int? id)
       { 
           var dropDownTreeData = 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(dropDownTreeData);
       }
   
       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" }
       };
   }

   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 DropDownTree in Razor Pages example.

Binding to a PageModel Property

To bind the DropDownTree to a property from the PageModel, follow the next steps:

1. Add a property to the PageModel that must bind to the DropDownTree.

   C#

       public class IndexModel : PageModel
       {
           [BindProperty]
           public string Employee { get; set; }
   
           public void OnGet()
           {
               Employee = "John"; 
           }
       }

2. Declare the PageModel at the top of the page.

   C#

       @page
       @model IndexModel

3. Bind the DropDownTree to the property using the DropDownTreeFor() configuration.

   Razor

       @page
       @model IndexModel
   
       @inject Microsoft.AspNetCore.Antiforgery.IAntiforgery Xsrf
       @Html.AntiForgeryToken()
   
       @(Html.Kendo().DropDownTreeFor(m => m.Employee))

   Razor

       @page
       @model IndexModel
   
       @inject Microsoft.AspNetCore.Antiforgery.IAntiforgery Xsrf
       @Html.AntiForgeryToken()
       @addTagHelper *, Kendo.Mvc
   
       <kendo-dropdowntree for="Employee">
       </kendo-datetimepicker>

See Also

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