I have not tried it but it seems that that ClassicBorderDecorator
is defined in PresentationFramework.Classic.dll
(not in PresentationFramework.Aero.dll
). So you need to fix your reference and change your namespace definition:
<Application
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Classic"
x:Class="Application" StartupUri="MainWindow.xaml">