Dispose a pen

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

public class Form1 : Form {

    protected override void OnPaint(PaintEventArgs e) {
        Graphics g = e.Graphics;
        g.FillRectangle(Brushes.White, this.ClientRectangle);

        Pen p = new Pen(Color.Black);
        g.DrawLine(p, 0, 0, 100, 100);
        p.Dispose();
    }
    public static void Main() {
        Application.Run(new Form1());
    }
}