How to use the LinearGradientBrush in c#.Net

///////////////////    CODE   //////////////////////////

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D;

namespace _124
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void panel1_Click(object sender, EventArgs e)
        {
           LinearGradientBrush lgb=new LinearGradientBrush(new Point(20,20),new Point(70,70),Color.Blue,Color.Red);
            Graphics g=panel1.CreateGraphics();
            g.FillRectangle(lgb,20,20,500,500);
        }
    }
}

////////////////   OUTPUT   /////////////////////////

--
/\/ir@\/ <(.'.)>