¿Que hago mal?, o, ¿donde creo un objeto Graphics visible en toda una clase?

Hola, aqui tengo un codigo que no se como hacer que funcione. Trato de

un objeto graphics llamado lienzo a partir de un objeto pictureBox1 y
acceder a el desde un metodo llamado Button1_Click.

El caso es que el objeto creado desde el constructor no es visible desde

metodo Button1_Click, lo he probado todo y estoy convencido de que es una
chorrada, entonces, ¿que hago mal? (o que no hago).

Gracias,

Eric

Aqui esta el codigo para los que me lean,

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

namespace CallCenter
{
public class clsLogin : System.Windows.Forms.Form
{
private System.Windows.Forms.PictureBox pictureBox1;
private System.Windows.Forms.Button button1;
private System.ComponentModel.Container components = null;
public clsLogin()
{
InitializeComponent();
lienzo=new pictureBox1.CreateGraphics(); //
<- esta es la linea donde

e inicializo el objeto
}
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}

#region Windows Form Designer generated code
private void InitializeComponent()
{
this.pictureBox1 = new System.Windows.Forms.PictureBox();
this.button1 = new System.Windows.Forms.Button();
this.SuspendLayout();
this.pictureBox1.BorderStyle > System.Windows.Forms.BorderStyle.FixedSingle;
this.pictureBox1.Location = new System.Drawing.Point(64, 80);
this.pictureBox1.Name = "pictureBox1";
this.pictureBox1.Size = new System.Drawing.Size(280, 160);
this.pictureBox1.TabIndex = 0;
this.pictureBox1.TabStop = false;
this.button1.Location = new System.Drawing.Point(304, 256);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(80, 32);
this.button1.TabIndex = 1;
this.button1.Text = "button1";
this.button1.Click += new System.EventHandler(this.button1_Click);
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(400, 302);
this.Controls.AddRange(new System.Windows.Forms.Control[] {
this.button1,
this.pictureBox1});
this.Name = "clsLogin";
this.Text = "Logon usuario";
this.ResumeLayout(false);

}
#endregion
[STAThread]
static void Main()
{
Application.Run(new clsLogin());
}
private void button1_Click(object sender, System.EventArgs e)
{
Pen lapizRojo=new Pen(Color.Red);
lienzo.DrawLine(lapizRojo,0,0,100,100);
<- y aqui no la
ve
}
}
}