C# areo glass on WPF

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C#

this is my code I found on the web

private void Window_Loaded(object sender, RoutedEventArgs e)
        {

IntPtr hwnd = new WindowInteropHelper(this).Handle;

    //Set backgroung to black
    HwndSource source = HwndSource.FromHwnd(hwnd);
    source.CompositionTarget.BackgroundColor = Color.FromArgb(0, 0, 0, 0);

    //Set glass
    VistaControls.DWM.DWMManager.EnableGlassSheet(hwnd);

        }

the problem with this code is

//Set glass
    VistaControls.DWM.DWMManager.EnableGlassSheet(hwnd);

I get this error
Error 1 The name 'VistaControls' does not exist in the current context Z:\areo\areo\MainWindow.xaml.cs 38 2 areo

And I was wondering if I missed something, the form is meant to look like glass areo