An abstraction layer to simplify the way that you can put interactive FrameworkElements on the TitleBar.
public MainWindow()
{
this.InitializeComponent();
ExtendsContentIntoTitleBar = true;
SetTitleBar(AppTitleBar);
DragRegions = new DragRegions(this, AppTitleBar);
DragRegions.NonDragElements = new FrameworkElement[] { SearchBox };
}