recaptcha in Picturebox

string code;

private void CreateImage()
{
	code = GetRandomText();

	Bitmap bitmap = new Bitmap(200, 50, PixelFormat.Format32bppArgb);
	Graphics g = Graphics.FromImage(bitmap);
	Pen pen = new Pen(Color.Yellow);
	Rectangle rect = new Rectangle(0, 0, 200, 50);
	SolidBrush b = new SolidBrush(Color.Black);
	SolidBrush blue = new SolidBrush(Color.Blue);
	int counter = 0;

	g.DrawRectangle(pen, rect);
	g.FillRectangle(b, rect);

	for (int i = 0; i < code.Length; i++)
	{
		g.DrawString(code[i].ToString(), new Font("Verdena", 10 + rand.Next(14, 18)), blue, new PointF(10 + counter, 10));

		counter += 20;

		int red = 0;
		int white = 11;

		while (white <= 100)
		{
			g.FillRectangle(Brushes.White, 0, red, 200, 10);
			g.FillRectangle(Brushes.White, 0, white, 200, 10);

			red += 20;
			white += 20;
		}
	}

	DrawRandomLines(g);

	pictureBox1.Image = bitmap;

/*	if (File.Exists("bitmap"))
	{
		try
		{
			File.Delete("bitmap");
			bitmap.Save("bitmap");
		}
		catch
		{
		}
	}
*/

//	g.Dispose();
//	bitmap.Dispose();
//	pictureBox1.Image = Image.FromFile(bitmap);
}

private void DrawRandomLines(Graphics g)
{
	SolidBrush green = new SolidBrush(Color.Green);

	for (int i = 0; i < 20; i++)
	{
		g.DrawLines(new Pen(green, 2), GetRandomPoints());
	}
}

private Point[] GetRandomPoints()
{
	Point[] points = { new Point(rand.Next(10, 150), rand.Next(10, 150)), new Point(rand.Next(10, 100), rand.Next(10, 100)) };
	
	return points;
}

private string GetRandomText()
{
	StringBuilder randomText = new StringBuilder();

	if (String.IsNullOrEmpty(code))
	{
		string alphabets = "abcdefghijklmnopqrstuvwxyz1234567890";
		Random r = new Random();
		
		for (int j = 0; j <= 5; j++)
		{
			randomText.Append(alphabets[r.Next(alphabets.Length)]);
		}

		code = randomText.ToString();
	}
	
	return code;
}