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The ItemDataBound event occurs for each new item that is added to the Items collection of the dropdownlist when it is bound. This event only occurs if the items are loaded from a data source (the DataSource or DataSourceID property is set).

For each item that is added from a data source, the following events occur:

  1. A new item is created and added to the Items collection.

  2. The Text and Value properties of the item are set, based on the data.

  3. The ItemDataBound event occurs.

The ItemDataBound event handler receives two arguments:

  1. The RadMultiColumnComboBox that is loading items. This argument is of type object, but can be cast to the RadMultiColumnComboBox type.

  2. An EventArgs object. This object has an Item property, which provides access to the item that was just bound. This item, in turn, has a DataItem property, which lets you access the item in the data source to which the RadMultiColumnComboBox is being bound.

Use the ItemDataBound event handler to make changes to items as they are bound to the data. For example, you can set custom attributes based on other fields in the DataItem:

<telerik:RadMultiColumnComboBox DataTextField="Name" DataValueField="Id" runat="server" ID="RadMultiColumnComboBox1" OnItemDataBound="RadMultiColumnComboBox1_ItemDataBound">
        <telerik:MultiColumnComboBoxColumn Field="Id" Width="30px" Title="Id" />
        <telerik:MultiColumnComboBoxColumn Field="Title" Width="250px">
                Position of <strong>#:data.Title#</strong>: #: attributes.customAttrText #
protected void RadMultiColumnComboBox1_ItemDataBound(object sender, RadMultiColumnComboBoxItemEventArgs e)
    var dataItem = e.Item.DataItem as MyClass;
    e.Item.Attributes.Add("customAttrText", "#" + dataItem.Id);

protected void Page_Load(object sender, EventArgs e)
    var items = Enumerable.Range(0, 10).Select(x => new MyClass() { Id = x, Name = "Name " + x, Title = "Title " + x });
    RadMultiColumnComboBox1.DataSource = items;

public class MyClass
    public int Id { get; set; }
    public string Name { get; set; }
    public string Title { get; set; }
    Protected Sub RadMultiColumnComboBox1_ItemDataBound(ByVal sender As Object, ByVal e As RadMultiColumnComboBoxItemEventArgs)
        Dim dataItem = TryCast(e.Item.DataItem, [MyClass])
        e.Item.Attributes.Add("customAttrText", "#" & dataItem.Id)
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        Dim items = Enumerable.Range(0, 10).[Select](Function(x) New [MyClass]() With {
            .Id = x,
            .Name = "Name " & x,
            .Title = "Title " & x
        RadMultiColumnComboBox1.DataSource = items
    End Sub

    Public Class [MyClass]
        Public Property Id As Integer
        Public Property Name As String
        Public Property Title As String
    End Class
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