Drawing Pie Chart

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;

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

        private void btn_show_Click(object sender, EventArgs e)
        {
            // Create a Graphics object
            Graphics g = this.CreateGraphics();
            g.Clear(this.BackColor);

            // get the current value of start and sweep angles
            float startAngle = (float)Convert.ToDouble(textBox1.Text);
            float sweepAngle = (float)Convert.ToDouble(textBox2.Text);

            // Create a pen
            Pen writePen = new Pen(Color.Blue, 1);

            // Draw pie
            g.DrawPie(writePen, 20, 20, 100, 100, startAngle, sweepAngle);

            // dispose of objects
            writePen .Dispose();
            g.Dispose();
        }
    }
}