Csharp/CSharp Tutorial/2D/Mouse Draw

Basic Paint Form: click mouse button to add the an Ellipse

using System;
using System.Drawing;
using System.Collections;
using System.ruponentModel;
using System.Windows.Forms;
using System.Data;
using System.Drawing.Drawing2D;
public class FormBasicPaintMouseClick : System.Windows.Forms.Form
{
  private System.ruponentModel.Container components = null;
  private System.Windows.Forms.Button btnRenderedButton;
  private System.Windows.Forms.Button btnRenderToOtherButton;
  private ArrayList myPts = new ArrayList();
  public FormBasicPaintMouseClick()
  {
    InitializeComponent();
  }
  protected override void Dispose( bool disposing )
  {
    if( disposing )
    {
      if (components != null) 
      {
        components.Dispose();
      }
    }
    base.Dispose( disposing );
  }
  private void InitializeComponent()
  {
    this.btnRenderedButton = new System.Windows.Forms.Button();
    this.btnRenderToOtherButton = new System.Windows.Forms.Button();
    this.SuspendLayout();
    // 
    // btnRenderedButton
    // 
    this.btnRenderedButton.Location = new System.Drawing.Point(168, 120);
    this.btnRenderedButton.Name = "btnRenderedButton";
    this.btnRenderedButton.Size = new System.Drawing.Size(112, 136);
    this.btnRenderedButton.TabIndex = 0;
    this.btnRenderedButton.Text = "Click on other button!";
    // 
    // btnRenderToOtherButton
    // 
    this.btnRenderToOtherButton.Location = new System.Drawing.Point(168, 8);
    this.btnRenderToOtherButton.Name = "btnRenderToOtherButton";
    this.btnRenderToOtherButton.Size = new System.Drawing.Size(112, 56);
    this.btnRenderToOtherButton.TabIndex = 1;
    this.btnRenderToOtherButton.Text = "Render to button";
    // 
    // FormBasicPaintMouseClick
    // 
    this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
    this.ClientSize = new System.Drawing.Size(292, 273);
    this.Controls.Add(this.btnRenderToOtherButton);
    this.Controls.Add(this.btnRenderedButton);
    this.Name = "FormBasicPaintMouseClick";
    this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
    this.Text = "Basic Paint Form";
    this.MouseDown += new System.Windows.Forms.MouseEventHandler(this.FormBasicPaintMouseClick_MouseDown);
    this.Paint += new System.Windows.Forms.PaintEventHandler(this.FormBasicPaintMouseClick_Paint);
    this.ResumeLayout(false);
  }
  [STAThread]
  static void Main() 
  {
    Application.Run(new FormBasicPaintMouseClick());
  }
  private void FormBasicPaintMouseClick_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
  {
    myPts.Add(new Point(e.X, e.Y));
    Invalidate();
  }
  private void FormBasicPaintMouseClick_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);
  }
}