How to restrict the opening of RibbonContextMenu in WPF Ribbon control?

<syncfusion:Ribbon x:Name="ribbon" RibbonContextMenuOpening="Ribbon_ContextMenuOpening">
      <syncfusion:RibbonTab Caption="Home" >
            <syncfusion:RibbonBar Header="Respond">
                  <syncfusion:RibbonButton SizeForm="Large" Label="Reply"/>
                  <syncfusion:RibbonButton SizeForm="Small" Label="ReplyAll"/>
                  <syncfusion:RibbonButton SizeForm="Small" Label="Forward"/>
            </syncfusion:RibbonBar>
      </syncfusion:RibbonTab>
      <syncfusion:RibbonTab Caption="Send/Receive" >
            <syncfusion:RibbonBar Header="Download">
                  <syncfusion:RibbonButton SizeForm="Small" Label="Show Progress"/>
                  <syncfusion:RibbonButton SizeForm="Small" Label="CancelAll"/>
                  <syncfusion:RibbonButton SizeForm="Large" Label="Download Headers"/>
            </syncfusion:RibbonBar>
       </syncfusion:RibbonTab>
</syncfusion:Ribbon>

private void Ribbon_ContextMenuOpening(object sender, ContextMenuEventArgs e)
{
   e.Handled = true;
}