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CheckBoxes RadioButton Behavior

You may want the checkbox to exhibit a non-standard, RadioButton behavior, where only one checkbox may be selected at a time and all previous checkbox selections are cleared. The example below defines the OnClientNodeChecked event. The clientNodeChecked() function that handles this event first retrieves the currently checked Node. Then checks if there is a previously checked Node in the "oldNode" global variable and unchecks it if so. The newly clicked Node is checked, and a reference to it is saved off in "oldNode" for later use the next time the OnClientNodeChecked event fires.

<script type="text/javascript" language="javascript">

    var oldNode;
    function clientNodeChecked(sender, eventArgs) {
        var node = eventArgs.get_node();

        if (oldNode != null) {

        oldNode = node;

    function pageLoad() {
        var tree = $find("<%= RadTreeView1.ClientID  %>");
        var checkedNodes = tree.get_checkedNodes();
        if (checkedNodes) {
            //this will ensure the correct behavior even if a node is checked server-side
            oldNode = checkedNodes[0];
<telerik:RadTreeView RenderMode="Lightweight" ID="RadTreeView1" runat="server" CheckBoxes="True" OnClientNodeChecked="clientNodeChecked">
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