public MainWindow()
        {
            InitializeComponent();

            Grid grid = new Grid();

            for (int i = 0; i < 10; i++)
            {
                ColumnDefinition columnDefinition = new ColumnDefinition();
                grid.ColumnDefinitions.Add(columnDefinition);
            }

            for (int i = 0; i < 4; i++)
            {
                RowDefinition rowDefinition = new RowDefinition();
                grid.RowDefinitions.Add(rowDefinition);
            }

            for (int i = 0; i < grid.ColumnDefinitions.Count; i++)
            {
                for (int j = 0; j < grid.RowDefinitions.Count; j++)
                {
                    Rectangle rectangle = new Rectangle();
                    rectangle.Tag = i + ":" + j;
                    rectangle.Stroke = new SolidColorBrush(Colors.Black);
                    rectangle.StrokeThickness = 1;
                    rectangle.HorizontalAlignment = HorizontalAlignment.Stretch;
                    rectangle.VerticalAlignment = VerticalAlignment.Stretch;
                    Grid.SetColumn(rectangle, i);
                    Grid.SetRow(rectangle, j);

                    grid.Children.Add(rectangle);
                }
            }

            //把第二列的第三行的矩形的背景设为红色
            foreach (Rectangle elemnet in grid.Children)
            {
                if (elemnet.Tag.ToString() == "1:2")
                {
                    elemnet.Fill = new SolidColorBrush(Colors.Red);
                }
            }
        }