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The OnClientCheckAllChecked client-side event occurs after the user click on the Check All check box. This event is added in 2013 Q3 release (Telerik.Web.UI.dll v.2013.3.1015).

The event handler receives two parameters:

  1. The instance of the combobox firing the event.

  2. An eventArgs parameter containing the following methods:

  • get_domEvent() returns the DOM event object of the drop-down opening.

  • get_checked() returns the value of the Check All check box after it is checked.

The example below shows how to get the value of the Check All check box:

<telerik:RadComboBox RenderMode="Lightweight" ID="RadComboBox1" runat="server" OnClientCheckAllChecked="OnClientCheckAllChecked"
    CheckBoxes="true" EnableCheckAllItemsCheckBox="true">
    <telerik:RadComboBoxItem Text="Item1" />
    <telerik:RadComboBoxItem Text="Item2" />
    <telerik:RadComboBoxItem Text="Item3" />
function OnClientCheckAllChecked(sender, args) {
    if (args.get_checked()) {
        alert('All items are checked.');
    else {
        alert('All items are unchecked.');
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