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The OnClientSelectedIndexChanged client-side event occurs immediately after the SelectedItem has been changed.

The event handler receives two parameters:

  1. The instance of the DropDownList firing the event.

  2. An eventArgs parameter containing the following method:

    • get_index() returns the index of the item, that has just been selected.

Use this event to respond to the newly selected item:

<script type="text/javascript">
    function OnClientSelectedIndexChanged(sender, eventArgs) {
        alert("You selected item with index : " + eventArgs.get_index());

        <telerik:DropDownListItem Text="Item 1" Value="1" />
        <telerik:DropDownListItem Text="Item 2" Value="2" />
        <telerik:DropDownListItem Text="Item 3" Value="3" />
        <telerik:DropDownListItem Text="Item 4" Value="4" />
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