生成随机验证码--C#

public void MakeCheckCode(string checkCodeCookieName, int len)
        {
            //这儿定义你期待产生的随机字母
            string[] arrLetter = new string[] { 
                                                   "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "L", "M", "N", "P", "Q", "R", 
                                                   "S", "T", "U", "V", "W", "X", "Y", "Z", "2", "3", "4", "5", "6", "7", "8", "9"
                                               };
            //随机颜色
            Color[] arrColor = new Color[] { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Green, Color.Brown, Color.DarkCyan, Color.Blue };
            //随机字体
            string[] arrFont = new string[] { "Arial", "Verdana" };

            Random romTemp = new Random();
            string strCheckCode = "";
            //产生随机字符串
            for (int i = 1; i <= len; i++)
            {
                strCheckCode = strCheckCode + arrLetter[romTemp.Next(arrLetter.Length)];
            }
            strCheckCode = strCheckCode.ToUpper();
            //将值写入cook
            HttpCookie cookTemp = new HttpCookie(checkCodeCookieName);
            cookTemp.Values.Add("CheckCode", strCheckCode);
            this.Context.Response.Cookies.Add(cookTemp);
            int intWidth = strCheckCode.Length * 13; //计算图片需要的宽度
            Bitmap bitmap1 = new Bitmap(intWidth,0x16);
            //绘图
            Graphics graphics1 = Graphics.FromImage(bitmap1);
            graphics1.Clear(Color.White);
            for (int i = 0; i < 5; i++)
            {
                //随机字母宽度
                int intLetterWidth = romTemp.Next(bitmap1.Width);
                //随机字母高度
                int intLetterHeight = romTemp.Next(bitmap1.Height);
                graphics1.DrawRectangle(new Pen(Color.DarkGray, 0f), intLetterWidth, intLetterHeight, 1, 1);
            }
            for (int i = 0; i < strCheckCode.Length; i++)
            {
                int num7 = romTemp.Next(arrColor.Length);
                int num8 = romTemp.Next(arrFont.Length);
                Font font1 = new Font(arrFont[num8], 10f, FontStyle.Bold);
                Brush brush1 = new SolidBrush(arrColor[num7]);
                graphics1.DrawString(strCheckCode.Substring(i, 1), font1, brush1, (float) (3 + (i * 11)), 3f);
            }
            graphics1.DrawRectangle(new Pen(Color.LightGray, 0f), 0, 0, bitmap1.Width - 1, bitmap1.Height - 1);
            graphics1.Dispose();
            System.IO.MemoryStream stream1 = new System.IO.MemoryStream();
            bitmap1.Save(stream1, System.Drawing.Imaging.ImageFormat.Gif);
            this.Context.Response.ClearContent();
            this.Context.Response.ContentType = "image/Gif";
            this.Context.Response.BinaryWrite(stream1.ToArray());
            bitmap1.Dispose();
            graphics1.Dispose();
        }