Bouncing Ball in C#

This program illustrates a bouncing Ball in C#

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace Ball_timer_2005
{
	/// <summary>
	/// Summary description for Form1.
	/// </summary>
	public class Form1 : System.Windows.Forms.Form
	{

		const int radius = 20;
		const int velocity = 5;

		int xC, yC, xDelta=10, yDelta=10, xSize, ySize;  // class level variables

		private System.Windows.Forms.Timer timer1;
		private System.ComponentModel.IContainer components;

		public Form1()
		{
			//
			// Required for Windows Form Designer support
			//
			InitializeComponent();

			//
			// TODO: Add any constructor code after InitializeComponent call
			this.ResizeRedraw = true;      // Tell form to redraw itself when resized
			timer1.Start();
			Form1_Resize(this, EventArgs.Empty);  // Force a Resize Event as pgm starts
			//
		}

		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

		#region Windows Form Designer generated code
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
			this.components = new System.ComponentModel.Container();
			this.timer1 = new System.Windows.Forms.Timer(this.components);
			// 
			// timer1
			// 
			this.timer1.Enabled = true;
			this.timer1.Interval = 25;
			this.timer1.Tick += new System.EventHandler(this.timer1_Tick);
			// 
			// Form1
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
			this.ClientSize = new System.Drawing.Size(292, 273);
			this.Name = "Form1";
			this.Text = "Bouncing Ball";
			this.Resize += new System.EventHandler(this.Form1_Resize);

		}
		#endregion

		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
		}



		private void Form1_Resize(object sender, System.EventArgs e)
		{
			xSize = this.ClientSize.Width;   // Set current window size
			ySize = this.ClientSize.Height;
			xC = xSize/2;                    // Place ball in center of window 
			yC = ySize/2;
			DrawBall();                       // Draw the ball in the window		
		}

		private void timer1_Tick(object sender, System.EventArgs e)
		{
			DrawBall();                       // Draw ball in next frame of animation		
		}

		private void DrawBall()
		{
			Graphics g = this.CreateGraphics();
			Brush b = new SolidBrush(this.BackColor);
			g.FillEllipse(b, xC-radius, yC-radius, 2*radius, 2*radius); //erase old ball
			xC += xDelta;                                                   //move ball
			yC += yDelta;
			if ((xC+radius >= ClientSize.Width) || (xC - radius <= 0)) //check for wall hits
				xDelta = -xDelta;
			if ((yC+radius >= ClientSize.Height) || (yC - radius <= 0))
				yDelta = -yDelta;
			b = new SolidBrush(Color.Red);                               // draw new ball
			g.FillEllipse(b, xC-radius, yC-radius, 2*radius, 2*radius);
			b.Dispose();
			g.Dispose();
		}

	}
}