Adding an Image to WPToolkit custom MessageBox in WP8

Image image = new Image();
            image.Height = 250;
            image.Width = 300;
            image.VerticalAlignment = System.Windows.VerticalAlignment.Center;
            image.HorizontalAlignment = System.Windows.HorizontalAlignment.Center;
            image.Margin = new Thickness(0, 12, 0, 12);
            image.Source = new BitmapImage() { UriSource = new Uri(@"/Assets/AppBar/AddToCart.png") };
            CustomMessageBox dialogBox = new CustomMessageBox()
            {
                Title = "Add to cart?",
                FontSize = 38,
                FontWeight = FontWeights.Thin,
                Margin = new Thickness(0,0,0,0),
                Content = image,
                LeftButtonContent = "Yes",
                RightButtonContent = "Cancel",
            };