Programmatic drawing with Silverlight Part 2: C#

In one of my previous posts I explored how programmatic drawing with Silverlight 1.0/JavaScript worked. It was done by constructing a XAML string and inserting it into the XAML hierarchy. Not a nice way of doing things, imho.

Fortunately Silverlight 1.1 alpha offers the possibility to use C#. This way there’s no need to construct strings anymore because the drawing API can be used for drawing. This is the same code I used in my previous post, but ported to C#:

Note Some things have changed in Silverlight 2 Beta 1:

• [Scriptable] on methods changed to [ScriptableMember()]
• Removed [Scriptable] on the class
• Changed the managed code scriptable object registration from WebApplication.Current.RegisterScriptableObject(”basic”, this);
  to

  HtmlPage.RegisterScriptableObject(”basic”, this);

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Browser;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Net;

namespace Whirl2
{
    public partial class Page : UserControl
    {
        public Page()
        {
            InitializeComponent();

            HtmlPage.RegisterScriptableObject("basic", this);  

            drawWhirl(3);
        }

        [ScriptableMember()]
        public void drawWhirl(uint numSides)
        {
            double[] x = new double[numSides + 1];
            double[] y = new double[numSides + 1];
            DateTime startTime = DateTime.Now;
            uint scaleFactor = 275;
            uint centerX = 300;
            uint centerY = 300;
            uint numLinesDrawn = 0;
            double rotAngle = 0.05;
            double rotAngleSin = Math.Sin(rotAngle);
            double rotAngleCos = Math.Cos(rotAngle);
            double a = (Math.PI * (1 - 2 / (double)numSides));
            double c = Math.Sin(a) / (rotAngleSin + Math.Sin(a + rotAngle));
            Canvas layoutRoot = FindName("LayoutRoot") as Canvas;

            layoutRoot.Children.Clear();

            for (uint k = 0; k <= numSides; k++)
            {
                double t = (2 * k + 1) * Math.PI / (double)numSides;
                x[k] = Math.Sin(t);
                y[k] = Math.Cos(t);
            }

            for (uint n = 1; n < 64; n++)
            {
                Point previousPoint = new Point();
                previousPoint.X = (x[0] * scaleFactor) + centerX;
                previousPoint.Y = (y[0] * scaleFactor) + centerY;

                for (uint l = 0; l <= numSides; l++)
                {
                    Point newPoint = new Point();
                    newPoint.X = (x[l] * scaleFactor) + centerX;
                    newPoint.Y = (y[l] * scaleFactor) + centerY;

                    Line line = new Line();
                    line.X1 = previousPoint.X;
                    line.Y1 = previousPoint.Y;
                    line.X2 = newPoint.X;
                    line.Y2 = newPoint.Y;
                    line.StrokeThickness = 1;
                    SolidColorBrush stroke = new SolidColorBrush();
                    stroke.Color = Colors.Black;
                    line.Stroke = stroke;

                    layoutRoot.Children.Add(line);

                    numLinesDrawn++;

                    previousPoint = newPoint;
                }

                for (uint m = 0; m <= numSides; m++)
                {
                    double z = x[m];
                    x[m] = (x[m] * rotAngleCos - y[m] * rotAngleSin) * c;
                    y[m] = (z * rotAngleSin + y[m] * rotAngleCos) * c;
                }
            }

            HtmlElement divInfo = HtmlPage.Document.GetElementById("divInfo");

            divInfo.SetAttribute("innerHTML",
                "<strong>Number of sides:</strong> " + numSides + "<br>" +
                "<strong>Number of lines drawn:</strong> " + numLinesDrawn + "<br>" +
                "<strong>Time:</strong> " + ((DateTime.Now - startTime).Milliseconds) + " milliseconds");
        }
    }
}

Take a look and compare the performance to the JavaScript version. Not surprisingly, it’s much faster.

• Download the Visual Studio 2008 project files (.rar)