TreeList HtmlHelper Overview

The Telerik UI TreeList HtmlHelper for ASP.NET Core is a server-side wrapper for the Kendo UI TreeList widget.

The TreeList enables the display of self-referencing tabular data and allows sorting, filtering, and data editing.

• Demo page for the TreeList

Initializing the TreeList

The following example demonstrates how to define the TreeList by using the TreeList HtmlHelper.

The TreeList HtmlHelper distinguishes the root items based on the ParentId field. If the ParentId is set as .Nullable(true), root items with be items whose ParentId field values are null. If the ParentId is not nullable (.Nullable(false)), root items will be items which have a default value for their data type.

    public class EmployeeViewModel
    {
        // The Id.
        public int EmployeeID { get; set; }

        public string FirstName { get; set; }

        public string LastName { get; set; }

        // A nullable ParentId.
        public int? ReportsTo { get; set; }

        public string Address { get; set; }

        // This is a case-sensitive property. Define it only if you want to use lazy-loading.
        // If it is not defined, the TreeList will calculate and assign its value on the client.
        public bool hasChildren { get; set; }
    }

 public JsonResult All([DataSourceRequest] DataSourceRequest request)
    {
        var result = GetDirectory().ToTreeDataSourceResult(request,
            e => e.EmployeeId,
            e => e.ReportsTo,
            e => e
        );

        return Json(result, JsonRequestBehavior.AllowGet);
    }

@(Html.Kendo().TreeList<Kendo.Mvc.Examples.Models.TreeList.EmployeeDirectoryModel>()
    .Name("treelist")
    .Columns(columns =>
    {
        columns.Add().Field(f => f.FirstName).Width(250).Title("First Name");
        columns.Add().Field(e => e.LastName).Title("Last Name");
        columns.Add().Field(e => e.Position);
        columns.Add().Field(e => e.Extension).Title("Ext").Format("{0:#}");
    })
    .DataSource(dataSource => dataSource
        .Read(read => read.Action("Index", "EmployeeDirectory"))
        .Model(m => {
            m.Id(f => f.EmployeeId);
            m.ParentId(f => f.ReportsTo).Nullable(true);
            m.Field(f => f.FirstName);
            m.Field(f => f.LastName);
            m.Field(f => f.ReportsTo);
        })
    )
)

Basic Configuration

The following example demonstrates the basic configuration for the TreeList HtmlHelper.

    public JsonResult All([DataSourceRequest] DataSourceRequest request)
    {
        var result = GetDirectory().ToTreeDataSourceResult(request,
            e => e.EmployeeId,
            e => e.ReportsTo,
            e => e
        );

        return Json(result, JsonRequestBehavior.AllowGet);
    }

    public JsonResult Destroy([DataSourceRequest] DataSourceRequest request, EmployeeDirectoryModel employee)
    {
        // Delete from database. Return the deleted item in an array and call the ToTreeDataSourceResult() method.
        return Json(new[] { employee }.ToTreeDataSourceResult(request, ModelState));
    }

    public JsonResult Create([DataSourceRequest] DataSourceRequest request, EmployeeDirectoryModel employee)
    {
        // Create in the database. Return the created item with an Id/ParentId fields in an array and call the ToTreeDataSourceResult() method.
        return Json(new[] { employee }.ToTreeDataSourceResult(request, ModelState));
    }

    public JsonResult Update([DataSourceRequest] DataSourceRequest request, EmployeeDirectoryModel employee)
    {
        // Update in database. Return the updated item in an array and call the ToTreeDataSourceResult() method.
        return Json(new[] { employee }.ToTreeDataSourceResult(request, ModelState));
    }

@(Html.Kendo().TreeList<Kendo.Mvc.Examples.Models.TreeList.EmployeeDirectoryModel>()
    .Name("treelist")
    .Toolbar(toolbar => toolbar.Create())
    .Columns(columns =>
    {
        columns.Add().Field(e => e.FirstName).Title("First Name").Width(220);
        columns.Add().Field(e => e.LastName).Title("Last Name").Width(100);
        columns.Add().Field(e => e.HireDate).Format("{0:MMMM d, yyyy}");
        columns.Add().Field(e => e.Extension).Title("Ext").Format("{0:#}");
        columns.Add().Title("Edit").Width(250).Command(c =>
        {
            c.Edit();
            c.Destroy();
        })
        .HtmlAttributes(new {
            style = "text-align: center;"
        });
    })
    .Editable(e=>e.Mode("inline"))
    .DataSource(dataSource => dataSource
        .Create(create => create.Action("Create", "EmployeeDirectory"))
        .Read(read => read.Action("All", "EmployeeDirectory"))
        .Update(update => update.Action("Update", "EmployeeDirectory"))
        .Destroy(delete => delete.Action("Destroy", "EmployeeDirectory"))
        .Model(m => {
            m.Id(f => f.EmployeeId);
            m.ParentId(f => f.ReportsTo).Nullable(false);
            m.Expanded(true);
        })
    )
    .Height(540)
)

Functionality and Features

• Ajax binding
• Editing
• Paging
• Multi-column headers

Events

You can subscribe to all TreeList events. For a complete example on basic TreeList events, refer to the demo on using the events of the TreeList.

    @(Html.Kendo().TreeList<KendoTreeListBinding.Models.EmployeeViewModel>()
        .Name("treelist")
        /* Other configurations. */
        .Events(events => {
            events.DataBinding("onDataBinding");
            events.DataBound("onDataBound");
        })
    )
    <script>
        function onDataBinding(e) {
            // Handle the dataBinding event.
            var treelist = this;
        }

        function onDataBound(e) {
            // Handle the dataBound event.
            var treelist = e.sender;
        }
    </script>

Referencing Existing Instances

To reference an existing Kendo UI TreeList instance, use the jQuery.data() configuration option. Once a reference is established, use the TreeList API to control its behavior.

@(Html.Kendo().TreeList<Kendo.Mvc.Examples.Models.TreeList.EmployeeDirectoryModel>()
    .Name("treelist")
    /* Other configurations. */
)
<script>
    $(function() {
        // The Name() of the TreeList is used to get its client-side instance.
        var treelist = $("#treelist").data("kendoTreeList");
    });
</script>

See Also

• Basic Usage of the TreeList HtmlHelper for ASP.NET Core (Demo)
• Server-Side API