Getting Started with the TreeList

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

You will initialize a TreeList control and bind it to data. Next, you will handle some of the TreeList events. Finally, you can run the sample code in Telerik REPL and continue exploring the components.

Sample Telerik UI for ASP.NET Core TreeList

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.

2. Declare the View Model

Declare the EmployeeDirectoryRemoteModel view model.

public class EmployeeDirectoryRemoteModel
{
    public int EmployeeId { get; set; }

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public int? ReportsTo { get; set; }

    public int? Extension { get; set; }

    public string Position { get; set; }

    public bool hasChildren { get; set; }
}

3. Initialize the TreeList

Use the TreeList HtmlHelper or TagHelper to add the component to a page and set some of its options.

Use the Name() configuration method to assign a name to the instance of the helper—this is mandatory as its value is used for the id and the name attributes of the TreeList element.
Configure the columns of the TreeList by binding them to the fields of the EmployeeDirectoryRemoteModel.
Add the DataSource() configuration option and set the Read end point and the Model option.

@using Kendo.Mvc.UI

<p class="title">Employees</p>
@(Html.Kendo().TreeList<MyApplication.Models.EmployeeDirectoryRemoteModel>()
    .Name("treelist")
    .Columns(columns =>
    {
        columns.Add().Field(f => f.FirstName).Width(250);
        columns.Add().Field(e => e.LastName);
        columns.Add().Field(e => e.Position);
        columns.Add().Field(e => e.Extension).Title("Ext").Format("{0:#}");
    })
    .DataSource(dataSource => dataSource
        .Read(read => read.Action("GetData", "Home"))
        .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);
        })
    )
)

@addTagHelper *, Kendo.Mvc

<p class="title">Employees</p>
<kendo-treelist name="treelist">
    <columns>
        <treelist-column field="FirstName" width="250px"></treelist-column>
        <treelist-column field="LastName"></treelist-column>
        <treelist-column field="Position"></treelist-column>
        <treelist-column field="Extension" title="Ext" format="{0:#}"></treelist-column>
    </columns>
    <treelist-datasource>
        <transport>
            <read url="@Url.Action("GetData","Home")"/>
        </transport>
        <schema data="Data" total="Total" errors="Errors">
            <treelist-model id="EmployeeId" parent-id="ReportsTo">
                <fields>
                    <field name="EmployeeId" type="number"></field>
                    <field name="ReportsTo" nullable="true"></field>
                    <field name="FirstName" type="string"></field>
                    <field name="LastName" type="string"></field>
                </fields>
            </treelist-model>
        </schema>
    </treelist-datasource>
</kendo-treelist>

4. Declare the Read Action

In the Home controller, declare the GetData action that you set to the DataSource Read configuration in the previous step.

public JsonResult GetData([DataSourceRequest] DataSourceRequest request, int? id)
{
    var data = GetEmployees();

    var result = data.Where(v => id.HasValue ? v.ReportsTo == id : v.ReportsTo == null)
        .Select(v => new
        {
            EmployeeId = v.EmployeeId,
            FirstName = v.FirstName,
            LastName = v.LastName,
            ReportsTo = v.ReportsTo,
            Position = v.Position,
            Extension = v.Extension,
            hasChildren = v.hasChildren,
        });

    return Json(result.ToTreeDataSourceResult(request));
}

public List<EmployeeDirectoryRemoteModel> GetEmployees()
{
    List<EmployeeDirectoryRemoteModel> data = new List<EmployeeDirectoryRemoteModel>();

    data.Add(new EmployeeDirectoryRemoteModel
    {
        EmployeeId = 1,
        FirstName = "Daryl",
        LastName = "Sweeney",
        Position = "CEO",
        Extension = 8253,
        ReportsTo = null,
        hasChildren = true
    });

    data.Add(new EmployeeDirectoryRemoteModel
    {
        EmployeeId = 2,
        FirstName = "Guy",
        LastName = "Wooten",
        Position = "Chief Technical Officer",
        Extension = 1155,
        ReportsTo = 1,
        hasChildren = false
    });

    data.Add(new EmployeeDirectoryRemoteModel
    {
        EmployeeId = 3,
        FirstName = "Buffy",
        LastName = "Weber",
        Position = "VP, Engineering",
        Extension = 8253,
        ReportsTo = 1,
        hasChildren = true
    });

    data.Add(new EmployeeDirectoryRemoteModel
    {
        EmployeeId = 4,
        FirstName = "Priscilla",
        LastName = "Frank",
        Position = "Chief Product Officer",
        Extension = 4183,
        ReportsTo = 3,
        hasChildren = false
    });

    data.Add(new EmployeeDirectoryRemoteModel
    {
        EmployeeId = 5,
        FirstName = "Anika",
        LastName = "Vega",
        Position = "Chief Process Officer",
        Extension = 6353,
        ReportsTo = 3,
        hasChildren = false
    });

    return data;
}

5. Handle the TreeList Events

The TreeList exposes various events that you can handle and further customize the functionality of the component. In this tutorial, you will use the DataBinding and DataBound events of the TreeList.

    @using Kendo.Mvc.UI

    @(Html.Kendo().TreeList<MyApplication.Models.EmployeeDirectoryRemoteModel>()
        .Name("treelist")
        .Columns(columns =>
        {
            columns.Add().Field(f => f.FirstName).Width(250);
            columns.Add().Field(e => e.LastName);
            columns.Add().Field(e => e.Position);
            columns.Add().Field(e => e.Extension).Title("Ext").Format("{0:#}");
        })
        .DataSource(dataSource => dataSource
            .Read(read => read.Action("GetData", "Home"))
            .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);
            })
        )
        .Events(events =>
        {
            events.DataBinding("onDataBinding");
            events.DataBound("onDataBound");
        })
    )

    <script>
        function onDataBinding(e) {
            console.log("TreeList data binding");
        }

        function onDataBound(e) {
            console.log("TreeList data bound");
        }
    </script>

    @addTagHelper *, Kendo.Mvc

    <kendo-treelist name="treelist"
        on-data-binding="onDataBinding"
        on-data-bound="onDataBound">
        <columns>
            <treelist-column field="FirstName" width="250px"></treelist-column>
            <treelist-column field="LastName"></treelist-column>
            <treelist-column field="Position"></treelist-column>
            <treelist-column field="Extension" title="Ext" format="{0:#}"></treelist-column>
        </columns>
        <treelist-datasource>
            <transport>
                <read url="@Url.Action("GetData","Home")"/>
            </transport>
            <schema data="Data" total="Total" errors="Errors">
                <treelist-model id="EmployeeId" parent-id="ReportsTo">
                    <fields>
                        <field name="EmployeeId" type="number"></field>
                        <field name="ReportsTo" nullable="true"></field>
                        <field name="FirstName" type="string"></field>
                        <field name="LastName" type="string"></field>
                    </fields>
                </treelist-model>
            </schema>
        </treelist-datasource>
    </kendo-treelist>

    <script>
        function onDataBinding(e) {
            console.log("TreeList data binding");
        }

        function onDataBound(e) {
            console.log("TreeList data bound");
        }
    </script>

For more examples, refer to the demo on using the events of the TreeList.

6. (Optional) Reference Existing TreeList Instances

To use the client-side API of the TreeList and build on top of its initial configuration, you need a reference to the TreeList instance. Once you get a valid reference, you can call the respective API methods:

Use the .Name() (id attribute) of the component instance to get a reference.

<script>
    var treelistReference = $("#TreeList").data("kendoTreeList"); // treelistReference is a reference to the existing instance of the helper.
</script>

Use the TreeList client-side API to control the behavior of the widget. In this example, you will use the autoFitColumn method to apply the minimum possible width to the second column of the TreeList.
```
<script>
    $(document).ready(function () {
        var treelistReference = $("#TreeList").data("kendoTreeList");

        treelistReference.autoFitColumn(1);
    })
</script>
```

For more information on referencing specific helper instances, see the Methods and Events article.

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 TreeList

Prerequisites

1. Prepare the CSHTML File

2. Declare the View Model

3. Initialize the TreeList

4. Declare the Read Action

5. Handle the TreeList Events

6. (Optional) Reference Existing TreeList Instances

Explore this Tutorial in REPL

Next Steps

See Also

Getting Started

Support Resources

Community