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Highlighting the Check All Option in RadComboBox on Expand


Product Version
RadComboBox for ASP.NET AJAX all


When using a RadComboBox with the EnableCheckAllItemsCheckBox option set to true, you might want to highlight the "Check All" checkbox automatically when the dropdown is expanded.

This KB article also answers the following questions:

  • How to automatically focus on the "Check All" option in RadComboBox?
  • How to visually highlight an item in RadComboBox upon expansion?
  • How to use JavaScript to modify RadComboBox items' appearance on certain events?


To highlight the "Check All" item when the RadComboBox is expanded, attach a client-side event handler to the OnClientDropDownOpened event. In this event handler, use JavaScript to add a custom CSS class or directly modify the style of the "Check All" checkbox container to visually distinguish it. The example below demonstrates how to add a hover effect class to the "Check All" checkbox container.

  1. Add the RadComboBox to your ASP.NET page and enable checkboxes and the "Check All" option.

  2. Define a JavaScript function that will be triggered on the OnClientDropDownOpened event. This function locates the "Check All" checkbox container using a jQuery selector and applies a custom class to it.

  3. Optionally, you can directly manipulate styles or attributes to achieve the desired visual effect.

<!DOCTYPE html>
    <title>RadComboBox Example</title>
    <form id="form1" runat="server">
        <telerik:RadScriptManager ID="RadScriptManager1" runat="server" />
        <telerik:RadComboBox ID="RadComboBox1" CheckBoxes="true" runat="server" OnClientDropDownOpened="onDropDownOpened" EnableCheckAllItemsCheckBox="true">
                <telerik:RadComboBoxItem Text="Item 1" />
                <telerik:RadComboBoxItem Text="Item 2" />
                <telerik:RadComboBoxItem Text="Item 3" />

    <script type="text/javascript">
        function onDropDownOpened(sender, eventArgs) {
            var checkall = $telerik.$('.rcbCheckAllItemsCheckBox').parent().parent();
            checkall.addClass("rcbCheckAllItemsHovered"); // Highlight the "Check All" item

This approach allows you to provide visual cues to users, making the UI more intuitive and user-friendly.

See Also

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