telerik:RadComboBox ID="RadComboBoxBroadField" runat="server" OnClientSelectedIndexChanged="fnLoadGeneralField" telerik:RadComboBox>

<telerik:RadComboBox ID="RadComboBoxGeneralField" runat="server" OnItemsRequested="RadComboBoxGeneralField_ItemsRequested" OnClientItemsRequested="ItemsLoaded" OnClientSelectedIndexChanged="fnLoadSpecificField" ></telerik:RadComboBox>

JavaScript:

<

script type="text/javascript">

//global variables for the general and specific comboboxes

var generalfieldCombo;

var specificfieldCombo;

function pageLoad()

{

// initialize the global variables

// in this event all client objects are already created and initialized

generalfieldCombo = $find("<%= RadComboBoxGeneralField.ClientID %>");

specificfieldCombo = $find(

"<%= RadComboBoxSpecificField.ClientID %>");

function

fnLoadGeneralField(combo, eventArqs)

{

    var item = eventArqs.get_item();

    generalfieldCombo.clearItems();

    generalfieldCombo.set_text(

"Loading...");

    // if a broad field is selected

    if (item.get_index() > 0)

    {

    // this will fire the ItemsRequested event of the

    // general field combobox passing the broadfieldID as a parameter

    generalfieldCombo.requestItems(item.get_value(), false);

}

else

{

    // the <Choose> item was chosen

    generalfieldCombo.set_text("N/A");

    generalfieldCombo.clearItems();

function ItemsLoaded(combo, eventArqs)

{

if (combo.get_items().get_count() > 0)

{

    // pre-select the first item

    combo.set_text(combo.get_items().getItem(0).get_text());

    combo.get_items().getItem(0).highlight();

}

else

    combo.set_text("N/A");

}

</script>

Server Code (VB.NET)
The BroadField is loaded through the code on page load using DataBind().

Protected

Sub RadComboBoxGeneralField_ItemsRequested(ByVal o As System.Object, ByVal e As Telerik.Web.UI.RadComboBoxItemsRequestedEventArgs) Handles RadComboBoxGeneralField.ItemsRequested

        LoadGeneralField(

CInt(e.Text))

End Sub

Public

Sub LoadGeneralField(ByVal intBroadFieldId As Integer)

Dim dsDB As New DataSet

If dsDB.Tables(0).Rows.Count > 0 Then

"GF_Desc"

    RadComboBoxGeneralField.DataValueField = "GF_Id"

    RadComboBoxGeneralField.DataSource = dsDB.Tables(0)

    RadComboBoxGeneralField.DataBind()

End If

End Sub