TreeView HtmlHelper Overview

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

The TreeView displays hierarchical data in a traditional tree structure.

Initializing the TreeView

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

@(Html.Kendo().TreeView()
    .Name("treeview")
    .DataTextField("Name")
    .DataSource(dataSource => dataSource
        .Read(read => read
            .Action("Read_TreeViewData", "TreeView")
        )
    )
)
public static IList<HierarchicalViewModel> GetHierarchicalData()
{
    var result = new List<HierarchicalViewModel>()
    {
        new HierarchicalViewModel() { ID = 1, ParendID = null, HasChildren = true, Name = "Parent item" },
        new HierarchicalViewModel() { ID = 2, ParendID = 1, HasChildren = true, Name = "Parent item" },
        new HierarchicalViewModel() { ID = 3, ParendID = 1, HasChildren = false, Name = "Item" },
        new HierarchicalViewModel() { ID = 4, ParendID = 2, HasChildren = false, Name = "Item" },
        new HierarchicalViewModel() { ID = 5, ParendID = 2, HasChildren = false, Name = "Item" }
    };

    return result;
}

public IActionResult Read_TreeViewData(int? id)
{
    var result = GetHierarchicalData()
        .Where(x => id.HasValue ? x.ParendID == id : x.ParendID == null)
        .Select(item => new {
            id = item.ID,
            Name = item.Name,
            expanded = item.Expanded,
            imageUrl = item.ImageUrl,
            hasChildren = item.HasChildren
        });

    return Json(result);
}

Basic Configuration

The following example demonstrates the basic configuration of the TreeView HtmlHelper and how to get the TreeView instance.

@(Html.Kendo().TreeView()
    .Name("treeview")
    .Checkboxes(true)
    .DragAndDrop(true)
    .DataTextField("Name")
    .DataSource(dataSource => dataSource
        .Read(read => read
            .Action("Employees", "TreeView")
        )
    )
)

<script type="text/javascript">
    $(function () {
        // The Name() of the TreeView is used to get its client-side instance.
        var treeview = $("#treeview").data("kendoTreeView");
        console.log(treeview);
    });
</script>

Functionality and Features

Events

The following example demonstrates the available TreeView events and how an event handler could be implemented for each of them. For a complete example on basic TreeView events, refer to the demo on using the events of the TreeView.

@(Html.Kendo().TreeView()
    .Name("treeview")
    .DataTextField("Name")
    .Checkboxes(true)
    .DragAndDrop(true)
    .DataSource(dataSource => dataSource
        .Read(read => read
            .Action("Employees", "TreeView")
        )
    )
    .Events(events => events
        .Change("onChange")
        .Select("onSelect")
        .Check("onCheck")
        .Collapse("onCollapse")
        .Expand("onExpand")
        .DragStart("onDragStart")
        .Drag("onDrag")
        .DragEnd("onDragEnd")
        .Drop("onDrop")
    )
)

<script type="text/javascript">
    function onChange(e) {
        console.log('Selected node changed to:', e.sender.select());
    }

    function onSelect(e) {
        console.log('Selected node:', e.node);
    }

    function onCheck(e) {
        console.log('Checked node:', e.node);
    }

    function onCollapse(e) {
        console.log('Collapsed node:', e.node);
    }

    function onExpand(e) {
        console.log('Expanded node:', e.node);
    }

    function onDragStart(e) {
        console.log('Started dragging:', e.sourceNode);
    }

    function onDrag(e) {
        console.log("Dragging:", e.sourceNode);
    }

    function onDragEnd(e) {
        console.log("Finished dragging:", e.sourceNode);
    }

    function onDrop(e) {
        console.log("Dropped:", e.sourceNode);
    }
</script>

See Also

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