Getting Started with the TreeView

This tutorial explains how to set up a basic Telerik UI for ASP.NET Core TreeView and highlights the major steps in the configuration of the component.

You will initialize a TreeView component with several items and checkboxes. Finally, you can run the sample code in Telerik REPL and continue exploring the components.

Sample Telerik UI for ASP.NET Core TreeView

Prerequisites

To successfully complete the tutorial, you need a project that is already configured to use the Telerik UI for ASP.NET Core components:

You can use the Telerik REPL playground and skip installing the components on your system and configuring a project.
You can prepare a Visual Studio project by following either of these guides:
- Creating a new pre-configured project for the Telerik UI for ASP.NET Core components from a project template.
- Manually configuring an existing project as described in the First Steps on Windows or First Steps on Mac articles.

1. Prepare the CSHTML File

The first step is to add the required directives at the top of the .cshtml document:

To use the Telerik UI for ASP.NET Core HtmlHelpers:
```
@using Kendo.Mvc.UI
```
To use the Telerik UI for ASP.NET Core TagHelpers:
```
@addTagHelper *, Kendo.Mvc
```

Optionally, you can structure the document by adding the desired HTML elements like headings, divs, paragraphs, and others.

    @using Kendo.Mvc.UI

    <h4>TreeView with items</h4>
    <div>

    </div>

    @addTagHelper *, Kendo.Mvc

    <h4>TreeView with items</h4>
    <div>

    </div>

2. Initialize the TreeView

Use the TreeView HtmlHelper or TagHelper to add the component to a page:

The Name() configuration method is mandatory as its value is used for the id and the name attributes of the TreeView element.
The Expanded() configuration of a TreeView item specifies whether it will be expanded initially.

@using Kendo.Mvc.UI

<h4>TreeView with a Placeholder</h4>
<div>
    @(Html.Kendo().TreeView()
        .Name("treeview")
        .Size(ComponentSize.Medium)
        .Items(items =>
        {
            items.Add().Text("Item 1").Expanded(true)
                .Items(subItems =>
                {
                    subItems.Add().Text("Item 1.1");
                    subItems.Add().Text("Item 1.2");
                    subItems.Add().Text("Item 1.3");
                });
            items.Add().Text("Item 2")
                .Items(subItems =>
                {
                    subItems.Add().Text("Item 2.1");
                    subItems.Add().Text("Item 2.2");
                    subItems.Add().Text("Item 2.3");
                });
            items.Add().Text("Item 3");
        })
    )
</div>

@addTagHelper *, Kendo.Mvc

<h4>TreeView with items</h4>
<div>
    <kendo-treeview auto-bind="true" load-on-demand="true" name="treeview" size="ComponentSize.Medium">
        <items>
            <treeview-item expanded="true" checked="false" text="Item 1" selected="false" enabled="true">
                <items>
                    <treeview-item expanded="false" checked="false" text="Item 1.1" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 1.2" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 1.3" selected="false" enabled="true">
                    </treeview-item>
</items>
            </treeview-item>
            <treeview-item expanded="false" checked="false" text="Item 2" selected="false" enabled="true">
                <items>
                    <treeview-item expanded="false" checked="false" text="Item 2.1" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 2.2" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 2.3" selected="false" enabled="true">
                    </treeview-item>
                </items>
            </treeview-item>
            <treeview-item expanded="false" checked="false" text="Item 3" selected="false" enabled="true">
            </treeview-item>
        </items>
    </kendo-treeview>
</div>

3. Select a Default Value

The next step is to enable the Checkboxes() of the TreeView and to configure two of the items as checked by default.

@using Kendo.Mvc.UI

<h4>TreeView with items</h4>
<div>
    @(Html.Kendo().TreeView()
        .Name("treeview")
        .Size(ComponentSize.Medium)
        .Checkboxes(true)
        .Items(items =>
        {
            items.Add().Text("Item 1").Expanded(true)
                .Items(subItems =>
                {
                    subItems.Add().Text("Item 1.1").Checked(true);
                    subItems.Add().Text("Item 1.2");
                    subItems.Add().Text("Item 1.3").Checked(true);
                });
            items.Add().Text("Item 2")
                .Items(subItems =>
                {
                    subItems.Add().Text("Item 2.1");
                    subItems.Add().Text("Item 2.2");
                    subItems.Add().Text("Item 2.3");
                });
            items.Add().Text("Item 3");
        })
    )
</div>

@addTagHelper *, Kendo.Mvc

<h4>TreeView with items</h4>
<div>
    <kendo-treeview auto-bind="true" load-on-demand="true" name="treeview" size="ComponentSize.Medium">
        <checkboxes enabled="true" />
        <items>
            <treeview-item expanded="true" checked="false" text="Item 1" selected="false" enabled="true">
                <items>
                    <treeview-item expanded="false" checked="true" text="Item 1.1" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 1.2" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="true" text="Item 1.3" selected="false" enabled="true">
                    </treeview-item>
</items>
            </treeview-item>
            <treeview-item expanded="false" checked="false" text="Item 2" selected="false" enabled="true">
                <items>
                    <treeview-item expanded="false" checked="false" text="Item 2.1" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 2.2" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 2.3" selected="false" enabled="true">
                    </treeview-item>
                </items>
            </treeview-item>
            <treeview-item expanded="false" checked="false" text="Item 3" selected="false" enabled="true">
            </treeview-item>
        </items>
    </kendo-treeview>
</div>

4. Handle a TreeView Event

The TreeView component provides convenient events for implementing your desired logic. In this tutorial, you will use the exposed Check() event to log a new entry in the browser's console.

@using Kendo.Mvc.UI

<h4>TreeView with items</h4>
<div>
    <script>
        function check(e) {
            console.log("Check :: " + $(e.node).text());
        }
    </script>   

    @(Html.Kendo().TreeView()
        .Name("treeview")
        .Size(ComponentSize.Medium)
        .Checkboxes(true)
        .Events(e => e.Check("check"))
        .Items(items =>
        {
            items.Add().Text("Item 1").Expanded(true)
                .Items(subItems =>
                {
                    subItems.Add().Text("Item 1.1").Checked(true);
                    subItems.Add().Text("Item 1.2");
                    subItems.Add().Text("Item 1.3").Checked(true);
                });
            items.Add().Text("Item 2")
                .Items(subItems =>
                {
                    subItems.Add().Text("Item 2.1");
                    subItems.Add().Text("Item 2.2");
                    subItems.Add().Text("Item 2.3");
                });
            items.Add().Text("Item 3");
        })
    )
</div>

@addTagHelper *, Kendo.Mvc

<h4>TreeView with items</h4>
<div>
    <script>
        function check(e) {
            console.log("Check :: " + $(e.node).text());
        }
    </script>   

    <kendo-treeview auto-bind="true" load-on-demand="true"
     name="treeview" size="ComponentSize.Medium" on-check="check">
        <checkboxes enabled="true" />
        <items>
            <treeview-item expanded="true" checked="false" text="Item 1" selected="false" enabled="true">
                <items>
                    <treeview-item expanded="false" checked="true" text="Item 1.1" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 1.2" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="true" text="Item 1.3" selected="false" enabled="true">
                    </treeview-item>
</items>
            </treeview-item>
            <treeview-item expanded="false" checked="false" text="Item 2" selected="false" enabled="true">
                <items>
                    <treeview-item expanded="false" checked="false" text="Item 2.1" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 2.2" selected="false" enabled="true">
                    </treeview-item>
                    <treeview-item expanded="false" checked="false" text="Item 2.3" selected="false" enabled="true">
                    </treeview-item>
                </items>
            </treeview-item>
            <treeview-item expanded="false" checked="false" text="Item 3" selected="false" enabled="true">
            </treeview-item>
        </items>
    </kendo-treeview>
</div>

5. (Optional) Reference Existing TreeView Instances

You can reference the TreeView instances that you have created and build on top of their existing configuration:

Use the id attribute of the component instance to establish a reference.

<script>
    var treeviewReference = $("#treeview").data("kendoTreeView"); // treeviewReference is a reference to the existing TreeView instance of the helper.
</script>

Use the TreeView client-side API to control the behavior of the widget. In this example, you will use the findByText and select methods to select an item.

<script>
    var treeviewReference = $("#treeview").data("kendoTreeView"); // treeviewReference is a reference to the existing TreeView instance of the helper.

     var node = treeviewReference.findByText("Item 2");
     treeviewReference.select(node);
</script>

Explore this Tutorial in REPL

You can continue experimenting with the code sample above by running it in the Telerik REPL server playground:

Getting Started with the TreeView

Prerequisites

1. Prepare the CSHTML File

2. Initialize the TreeView

3. Select a Default Value

4. Handle a TreeView Event

5. (Optional) Reference Existing TreeView Instances

Explore this Tutorial in REPL

Next Steps

See Also

Getting Started

Support Resources

Community