using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; public class MainForm : System.Windows.Forms.Form { private System.ComponentModel.Container components; private ArrayList myPts = new ArrayList(); public MainForm() { InitializeComponent(); CenterToScreen(); this.Text = "click on me"; } protected override void Dispose( bool disposing ) { if( disposing ) { if (components != null) { components.Dispose(); } } base.Dispose( disposing ); } private void InitializeComponent() { this.AutoScaleBaseSize = new System.Drawing.Size(5, 13); this.ClientSize = new System.Drawing.Size(292, 273); this.Text = "Form1"; this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.MainForm_MouseDown); this.Paint += new System.Windows.Forms.PaintEventHandler(this.MainForm_Paint); } static void Main() { Application.Run(new MainForm()); } private void MainForm_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e) { Graphics g = Graphics.FromHwnd(this.Handle); // Add to points collection. myPts.Add(new Point(e.X, e.Y)); Invalidate(); } private void MainForm_Paint(object sender, System.Windows.Forms.PaintEventArgs e) { Graphics g = e.Graphics; foreach(Point p in myPts) g.DrawEllipse(new Pen(Color.Green), p.X, p.Y, 10, 10); } }