public MainWindow()
{
InitializeComponent();
grid = Graph;// new VirtualCanvas();
grid.SmallScrollIncrement = new Size(_tileWidth + _tileMargin, _tileHeight + _tileMargin);
//Scroller.Content = grid;
object v = Scroller.GetValue(ScrollViewer.CanContentScrollProperty);
Canvas target = grid.ContentCanvas;
zoom = new MapZoom(target);
pan = new Pan(target, zoom);
rectZoom = new RectangleSelectionGesture(target, zoom, ModifierKeys.Control);
rectZoom.ZoomSelection = true;
autoScroll = new AutoScroll(target, zoom);
zoom.ZoomChanged += new EventHandler(OnZoomChanged);
grid.VisualsChanged += new EventHandler <VisualChangeEventArgs>(OnVisualsChanged);
ZoomSlider.ValueChanged += new RoutedPropertyChangedEventHandler <double>(OnZoomSliderValueChanged);
grid.Scale.Changed += new EventHandler(OnScaleChanged);
grid.Translate.Changed += new EventHandler(OnScaleChanged);
grid.Background = new SolidColorBrush(Color.FromRgb(0xd0, 0xd0, 0xd0));
grid.ContentCanvas.Background = Brushes.White;
AllocateNodes();
}