CSharp: Template Method Pattern

   /// <summary>
    /// Summary description for Triangle.
    /// Template Method Pattern 模板方法模式
    ///20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public abstract class Triangle
    {

        /// <summary>
        /// 
        /// </summary>
        private Point p1, p2, p3;
        /// <summary>
        /// 
        /// </summary>
        protected Pen pen;
        /// <summary>
        /// 
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <param name="c"></param>
        public Triangle(Point a, Point b, Point c)
        {
            p1 = a;
            p2 = b;
            p3 = c;
            pen = new Pen(Color.Black, 1);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="g"></param>
        public virtual void draw(Graphics g)
        {
            g.DrawLine(pen, p1, p2);
            Point c = draw2ndLine(g, p2, p3);
            closeTriangle(g, c);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="g"></param>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        public abstract Point draw2ndLine(Graphics g, Point a, Point b);
        /// <summary>
        /// 
        /// </summary>
        /// <param name="g"></param>
        /// <param name="c"></param>
        public void closeTriangle(Graphics g, Point c)
        {
            g.DrawLine(pen, c, p1);
        }
    }

   /// <summary>
    /// Summary description for StdTriangle.
    /// Template Method Pattern 模板方法模式
    ///20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public class StdTriangle : Triangle
    {

        /// <summary>
        /// 
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <param name="c"></param>
        public StdTriangle(Point a, Point b, Point c) : base(a, b, c) 
        { }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="g"></param>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        public override Point draw2ndLine(Graphics g, Point a, Point b)
        {
            g.DrawLine(pen, a, b);
            return b;
        }
    }

   /// <summary>
    /// Summary description for IsocelesTriangle.
    /// Template Method Pattern 模板方法模式
    ///20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public class IsocelesTriangle : Triangle
    {
        private Point newc;
        private int newcx, newcy;
        /// <summary>
        /// 
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <param name="c"></param>
        public IsocelesTriangle(Point a, Point b, Point c)
            : base(a, b, c)
        {
            float dx1, dy1, dx2, dy2, side1, side2;
            float slope, intercept;
            int incr;
            dx1 = b.X - a.X;
            dy1 = b.Y - a.Y;
            dx2 = c.X - b.X;
            dy2 = c.Y - b.Y;

            side1 = calcSide(dx1, dy1);
            side2 = calcSide(dx2, dy2);

            if (side2 < side1)
                incr = -1;
            else
                incr = 1;
            slope = dy2 / dx2;
            intercept = c.Y - slope * c.X;

            //move point c so that this is an isoceles triangle
            newcx = c.X;
            newcy = c.Y;
            while (Math.Abs(side1 - side2) > 1)
            {
                newcx = newcx + incr;    //iterate a pixel at a time until close
                newcy = (int)(slope * newcx + intercept);
                dx2 = newcx - b.X;
                dy2 = newcy - b.Y;
                side2 = calcSide(dx2, dy2);
            }
            newc = new Point(newcx, newcy);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="a"></param>
        /// <param name="b"></param>
        /// <returns></returns>
        private float calcSide(float a, float b)
        {
            return (float)Math.Sqrt(a * a + b * b);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="g"></param>
        /// <param name="b"></param>
        /// <param name="c"></param>
        /// <returns></returns>
        public override Point draw2ndLine(Graphics g, Point b, Point c)
        {
            g.DrawLine(pen, b, newc);
            return newc;
        }

    }

调用：

    /// <summary>
    /// Template Method Pattern 模板方法模式
    ///20220918
    /// geovindu,Geovin Du,涂聚文
    /// </summary>
    public partial class TemplateMethodPatternForm : Form
    {

        private ArrayList triangles;
        /// <summary>
        /// 
        /// </summary>
        private void init()
        {
            triangles = new ArrayList();
            StdTriangle t1 = new StdTriangle(new Point(10, 10),
                new Point(150, 50),
                new Point(100, 75));
            IsocelesTriangle t2 = new IsocelesTriangle(
                new Point(150, 100), new Point(240, 40),
                new Point(175, 150));
            triangles.Add(t1);
            triangles.Add(t2);
            Pic.Paint += new PaintEventHandler(TPaint);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void TPaint(object sender, System.Windows.Forms.PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            for (int i = 0; i < triangles.Count; i++)
            {
                Triangle t = (Triangle)triangles[i];
                t.draw(g);
            }
        }
        /// <summary>
        /// 
        /// </summary>
        public TemplateMethodPatternForm()
        {
            InitializeComponent();
            init();
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void TemplateMethodPatternForm_Load(object sender, EventArgs e)
        {

        }
    }

输出：