I have simple requirement to save layout to file on Close and load the layout when opened. But I am getting error on LoadLayout: root element is missing.

I tried doing into a simple sample and getting the same issue. I have TilesControl (contains 2 tiles) and 2 button to Save & Load layouts.

MemoryStream m = new MemoryStream();
private void Save_Click(object sender, RoutedEventArgs e)
        {
            TilesControl.SaveLayout(m);
        }

private void Load_Click(object sender, RoutedEventArgs e)
        {
            TilesControl.LoadLayout(m);
       //ERROR: Root element is missing.

       }

Please help on this.