public void HighLight(System.Windows.Media.DrawingContext dc)
{
System.Windows.Media.SolidColorBrush brush = new System.Windows.Media.SolidColorBrush(System.Windows.Media.Colors.Gray);
System.Windows.Media.Pen pen = new System.Windows.Media.Pen(brush, 1);
dc.DrawEllipse(brush, pen, new System.Windows.Point(x * 50 + 25, y * 50 + 25), 20, 20);
}