Data commit

Task/Animate-a-pendulum/C-sharp/animate-a-pendulum.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Drawing;
+using System.Windows.Forms;
+
+class CSharpPendulum
+{
+    Form _form;
+    Timer _timer;
+
+    double _angle = Math.PI / 2,
+           _angleAccel,
+           _angleVelocity = 0,
+           _dt = 0.1;
+
+    int _length = 50;
+
+    [STAThread]
+    static void Main()
+    {
+        var p = new CSharpPendulum();
+    }
+
+    public CSharpPendulum()
+    {
+        _form = new Form() { Text = "Pendulum", Width = 200, Height = 200 };
+        _timer = new Timer() { Interval = 30 };
+
+        _timer.Tick += delegate(object sender, EventArgs e)
+        {
+            int anchorX = (_form.Width / 2) - 12,
+                anchorY = _form.Height / 4,
+                ballX = anchorX + (int)(Math.Sin(_angle) * _length),
+                ballY = anchorY + (int)(Math.Cos(_angle) * _length);
+
+            _angleAccel = -9.81 / _length * Math.Sin(_angle);
+            _angleVelocity += _angleAccel * _dt;
+            _angle += _angleVelocity * _dt;
+
+            Bitmap dblBuffer = new Bitmap(_form.Width, _form.Height);
+            Graphics g = Graphics.FromImage(dblBuffer);
+            Graphics f = Graphics.FromHwnd(_form.Handle);
+
+            g.DrawLine(Pens.Black, new Point(anchorX, anchorY), new Point(ballX, ballY));
+            g.FillEllipse(Brushes.Black, anchorX - 3, anchorY - 4, 7, 7);
+            g.FillEllipse(Brushes.DarkGoldenrod, ballX - 7, ballY - 7, 14, 14);
+
+            f.Clear(Color.White);
+            f.DrawImage(dblBuffer, new Point(0, 0));
+        };
+
+        _timer.Start();
+        Application.Run(_form);
+    }
+}