# Binding to Array and ArrayList

Binding **RadTreeView** to a data source that implements **IEnumerable**, such as **Array** or **ArrayList**, can create a flat data structure as well as a hierarchy if the proper **ID** -> **ParentID** relationship is provided.

Here is a general outline of **IEnumerable** data binding:

1. Create the collection.

2. Add values to the collection and set the **DataSource** property of **RadTreeView** to the instance of the collection.

3. Call the **DataBind()** method.

The collection is automatically mapped to the **Text** property of the respective TreeView Node. The example below takes an array of strings as a data source.

> caption

![RadTreeView Binding to Array](https://www.telerik.com/products/aspnet-ajax/documentation/assets/5a76adf2eb7256bea3c39a59b507e82b/treeview_databindingarray01.png)

```C#
protected void Page_Load(object sender, EventArgs e)
{    
    if (!IsPostBack)    
    {
        string[] cars = new string[] {"Porsche Carrera","Ferrari F430","Aston Martin DB9"};
        RadTreeView1.DataSource = cars;        
        RadTreeView1.DataBind();    
    }
}
```

```VB.NET
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If Not IsPostBack Then
        Dim cars As String() = New String() {"Porsche Carrera", "Ferrari F430", "Aston Martin DB9"}
        RadTreeView1.DataSource = cars
        RadTreeView1.DataBind()
    End If
End Sub
```

If you have a collection (any collection implementing **ICollection** or **IEnumerable**) that contains objects (as opposed to simple values), you can take advantage of **DataTextField**, **DataNavigateUrlField**, and **DataValueField** properties to map object properties from the object directly to the **Text**, **NavigateUrl** or **Value** fields. If the **DataFieldID** and **DataFieldParentID** properties are set, **RadTreeView** will create a hierarchy of Nodes, determining the Root ones using the following algorithm:

> tip their **DataFieldParentID** property must be **null** if it is of nullable (e.g. **int?** ) or reference (e.g. **string** ) type.
>
> *example*
> **ID**  **ParentID**
> 1 (null)
> 2 1
>
> their **DataFieldParentID** property must return the **default value** if it is value type (e.g. **0** for **int** , **Guid.Empty** for **Guid** ).
>
> *example*
> **ID**  **ParentID**
> 1 0
> 2 1

> note To see hierarchical data binding to **IEnumerable** in action, please visit the [Hierarchical Data Binding](https://demos.telerik.com/aspnet-ajax/TreeView/Examples/Programming/DataBinding/DefaultCS.aspx) live demo.

If you need to map additional properties from the object, subscribe to the [NodeDataBound](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/server-side-programming/events/nodedatabound) event. The event arguments passed to the event, **e.NodeBound** and **e.NodeBound.DataItem**, hold the instance of the TreeView Node being bound and the **DataItem** associated with the TreeView Node. You can then map a property from the **DataItem** (make sure to cast the **DataItem** object to your respective data type first) to a property of the **RadTreeNode** class.

The example below creates a list of car objects, each with properties for Name, Price and URL. **DataTextField** is bound to "Name", **DataNavigateUrlField** is bound to "URL" and **DataValueField** is bound to "Price". Note that the [NodeDataBound](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/server-side-programming/events/nodedatabound) event handler sets the **Target** property of each Node to *\_self* so that the URL for each Node will display in a new window. When the Node is clicked, the **Text** and **Value** of the Node is displayed in the page title and the Node is selected. Navigation to the URL occurs automatically. Also notice that the [NodeDataBound](https://www.telerik.com/products/aspnet-ajax/documentation/controls/treeview/server-side-programming/events/nodedatabound) event handler sets the tooltip of the Node based on the Node **DataItem**. The **DataItem** is cast to the underlying Car object type.

> caption

![RadTreeView Binding to Array](https://www.telerik.com/products/aspnet-ajax/documentation/assets/9cb739cd16fcb678212162150b77ef34/treeview_databindingarray.png)

```C#
public partial class _Default : System.Web.UI.Page
{
   protected void Page_Load(object sender, EventArgs e)
   {
       if (!IsPostBack)
       {
           Car[] cars = new Car[] {
               new Car("Porsche Carrera", 79100, "http://www.google.com/search?q=Porsche"),
               new Car("Ferrari F430", 229955, "http://www.google.com/search?q=Ferrari"),
               new Car("Aston Martin DB9", 168000, "http://www.google.com/search?q=AstonMartin"),            
           };
           RadTreeView1.DataSource = cars;
           RadTreeView1.DataTextField = "Name";
           RadTreeView1.DataValueField = "Price";
           RadTreeView1.DataNavigateUrlField = "URL";
           RadTreeView1.DataBind();
       }
   }
   protected void RadTreeView1_NodeClick(object sender, Telerik.Web.UI.RadTreeNodeEventArgs e)
   {
       this.Title = e.Node.Text + " - Price:" + Convert.ToDouble(e.Node.Value).ToString("c");
       e.Node.Selected = true;
   }
   protected void RadTreeView1_NodeDataBound(object sender, Telerik.Web.UI.RadTreeNodeEventArgs e)
   {
       e.Node.Target = "_blank";       
       e.Node.ToolTip = "Top speed: " + (e.Node.DataItem as Car).TopSpeed.ToString() + "MPH";
   }
}

public class Car
{
   public Car(string name, double price, string url)
   {
       _name = name;
       _price = price;
       _url = url;
   }
   private string _name;
   public string Name
   {
       get { return _name; }
       set { _name = value; }
   }
   private double _price;
   public double Price
   {
       get { return _price; }
       set { _price = value; }
   }
   private string _url;
   public string URL
   {
       get { return _url; }
       set { _url = value; }
   }
} 
```

```VB.NET
Partial Public Class _Default
    Inherits System.Web.UI.Page
    
	Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        If Not IsPostBack Then
			Dim cars As Car() = New Car() {_
                      New Car("Porsche Carrera", 79100, "http://www.google.com/search?q=Porsche"), _
                      New Car("Ferrari F430", 229955, "http://www.google.com/search?q=Ferrari"), _
                      New Car("Aston Martin DB9", 168000, "http://www.google.com/search?q=AstonMartin")}
            
			RadTreeView1.DataSource = cars
            RadTreeView1.DataTextField = "Name"
            RadTreeView1.DataValueField = "Price"
            RadTreeView1.DataNavigateUrlField = "URL"
            RadTreeView1.DataBind()
        End If
    End Sub
	
    Protected Sub RadTreeView1_NodeClick(ByVal sender As Object, ByVal e As Telerik.Web.UI.RadTreeNodeEventArgs)
        Me.Title = e.Node.Text + " - Price:" + Convert.ToDouble(e.Node.Value).ToString("c")
        e.Node.Selected = True
    End Sub
	
    Protected Sub RadTreeView1_NodeDataBound(ByVal sender As Object, ByVal e As Telerik.Web.UI.RadTreeNodeEventArgs)
        e.Node.Target = "_blank"
        e.Node.ToolTip = "Top speed: " + (TryCast(e.Node.DataItem, Car)).TopSpeed.ToString() + "MPH"
    End Sub
End Class	

Public Class Car
    Public Sub New(ByVal name As String, ByVal price As Double, ByVal url As String)
        _name = name
        _price = price
        _url = url
    End Sub
    Private _name As String
    Public Property Name() As String
        Get
            Return _name
        End Get
        Set(ByVal value As String)
            _name = value
        End Set
    End Property
    Private _price As Double
    Public Property Price() As Double
        Get
            Return _price
        End Get
        Set(ByVal value As Double)
            _price = value
        End Set
    End Property
    Private _url As String
    Public Property URL() As String
        Get
            Return _url
        End Get
        Set(ByVal value As String)
            _url = value
        End Set
    End Property
End Class
	
	
```