生成随机验证码帮助类

public class VerifyCode
{
    /// <summary>
    /// 生成验证码
    /// </summary>
    /// <returns></returns>
    public byte[] GetVerifyCode()
    {
        int num = 80;
        int num2 = 30;
        int num3 = 16;
        string text = string.Empty;
        Color[] array = new Color[]
        {
            Color.Black, 
            Color.Red, 
            Color.Blue, 
            Color.Green, 
            Color.Orange, 
            Color.Brown, 
            Color.Brown, 
            Color.DarkBlue
        };
        string[] array2 = new string[]
        {
            "Times New Roman"
        };
        char[] array3 = new char[]
        {
            '2', 
            '3', 
            '4', 
            '5', 
            '6', 
            '8', 
            '9', 
            'a', 
            'b', 
            'd', 
            'e', 
            'f', 
            'h', 
            'k', 
            'm', 
            'n', 
            'r', 
            'x', 
            'y', 
            'A', 
            'B', 
            'C', 
            'D', 
            'E', 
            'F', 
            'G', 
            'H', 
            'J', 
            'K', 
            'L', 
            'M', 
            'N', 
            'P', 
            'R', 
            'S', 
            'T', 
            'W', 
            'X', 
            'Y'
        };
        Random random = new Random();
        for (int i = 0; i < 4; i++)
        {
            text += array3[random.Next(array3.Length)].ToString();
        }
        WriteSession("session_verifycode", Md5Helper.MD5(text.ToLower(), 16));
        Bitmap bitmap = new Bitmap(num, num2);
        Graphics graphics = Graphics.FromImage(bitmap);
        graphics.Clear(Color.White);
        for (int j = 0; j < 1; j++)
        {
            int x = random.Next(num);
            int y = random.Next(num2);
            int x2 = random.Next(num);
            int y2 = random.Next(num2);
            Color color = array[random.Next(array.Length)];
            graphics.DrawLine(new Pen(color), x, y, x2, y2);
        }
        for (int k = 0; k < text.Length; k++)
        {
            string familyName = array2[random.Next(array2.Length)];
            Font font = new Font(familyName, (float)num3);
            Color color2 = array[random.Next(array.Length)];
            graphics.DrawString(text[k].ToString(), font, new SolidBrush(color2), (float)k * 18f, 0f);
        }
        MemoryStream memoryStream = new MemoryStream();
        byte[] result;
        try
        {
            bitmap.Save(memoryStream, ImageFormat.Png);
            result = memoryStream.ToArray();
        }
        catch (Exception)
        {
            result = null;
        }
        finally
        {
            graphics.Dispose();
            bitmap.Dispose();
        }
        return result;
    }

    /// <summary>
    /// 写Session
    /// </summary>
    /// <param name="key">Session的键名</param>
    /// <param name="value">Session的键值</param>
    public void WriteSession(string key, string value)
    {
        WriteSession<string>(key, value);
    }

    /// <summary>
    /// 写Session
    /// </summary>
    /// <typeparam name="T">Session键值的类型</typeparam>
    /// <param name="key">Session的键名</param>
    /// <param name="value">Session的键值</param>
    public void WriteSession<T>(string key, T value)
    {
        bool flag = string.IsNullOrWhiteSpace(key);
        if (!flag)
        {
            HttpContext.Current.Session[key] = value;
        }
    }

}