How to Set DocMode for Specific C1DockTabItem in C1DockingTab for WPF

private void Button_Click(object sender, RoutedEventArgs e)
{
	var parent = tab1.Parent as C1DockTabControl;
	if (parent != null)
	{
		if (parent.Items.Count == 1)
		{
			parent.DockMode = DockMode.Sliding;
		}
		else
		{
			parent.Items.Remove(tab1);
			C1DockTabControl newDockTabCtrl = new C1DockTabControl();
			c1DockTabControl.Items.Add(newDockTabCtrl);
			newDockTabCtrl.Items.Add(tab1);
			newDockTabCtrl.DockMode = DockMode.Sliding:
		}
	}
}