set_allowMultiColumnSorting()

Sets whether multi-column sorting is enabled for the grid instance when bound on client-side. Review the toggleAllowMultiColumnSorting client-side method on this online demo for more details.

<telerik:RadGrid RenderMode="Lightweight" ID="RadGrid1" runat="server" AllowPaging="True"
    AllowSorting="true">
    <ClientSettings>
        <DataBinding SelectMethod="GetDataAndCount" Location="Service.svc"
            SortParameterType="Linq" FilterParameterType="Linq">
        </DataBinding>
    </ClientSettings>
    <MasterTableView DataKeyNames="OrderID" ClientDataKeyNames="OrderID"
        AllowMultiColumnSorting="true">
        <Columns>
            <telerik:GridBoundColumn DataField="ProductID" HeaderText="Product ID" DataType="System.Int32">
            </telerik:GridBoundColumn>
            <telerik:GridBoundColumn DataField="ProductName" HeaderText="Product Name" DataType="System.String">
            </telerik:GridBoundColumn>
            <telerik:GridBoundColumn DataField="UnitPrice" HeaderText="Unit Price" DataType="System.Decimal"
                DataFormatString="{0:C}">
            </telerik:GridBoundColumn>
            <telerik:GridCheckBoxColumn DataField="Discontinued" HeaderText="Discontinued" DataType="System.Boolean">
            </telerik:GridCheckBoxColumn>
        </Columns>
    </MasterTableView>
</telerik:RadGrid>
<br />
<asp:CheckBox ID="CheckBox1" runat="server" onclick="checkBoxClick(this);"
    Checked="true" Text="Toggle" />

function checkBoxClick(checkBox) {
var grid = $find('<%= RadGrid1.ClientID %>');
var masterTableView = grid.get_masterTableView();

// multi-column sorting will depend on the user interaction
masterTableView.set_allowMultiColumnSorting(checkBox.checked);
}