中文，字母，数字混合验证码

        /// 产生随机的混合编码-使用文字,字母,数字混合
        /// </summary>
        /// <param name="mixLength"></param>
        /// <returns></returns>
        private string GetRndMix(int mixLength)
        {
            String Vchar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z,好,哈,弹,平,合,下,天,人,无,有,中,木,不,字";
            String[] VcArray = Vchar.Split(',');

            String VMix = "";

            Random random = new Random();

            for (int i = 1; i <= mixLength; i++)
            {
                int iNum = 0;
                iNum = random.Next(VcArray.Length);
                VMix += VcArray[iNum];
            }

            return VMix;

        }

      /// <summary>
        /// 根据产生的随机数生成图象
        /// </summary>
        /// <param name="strCode"></param>
        private void CreateImg(string strCode, HttpContext context)
        {
            //也可以不用指定的图片，而是画一个背景图片
            Bitmap bitMapImage = new Bitmap(100, 25);
            Graphics graphicImage = Graphics.FromImage(bitMapImage);
            graphicImage.FillRectangle(new SolidBrush(Color.White), 0, 0, 100, 25);

            //设置画笔的输出模式
            graphicImage.SmoothingMode = SmoothingMode.HighSpeed;

            //添加文本字符串
            graphicImage.DrawString(strCode, new Font("Arial", 15, FontStyle.Bold), SystemBrushes.WindowText, new Point(0, 0));

            //画图片的前景噪音点
            Random randomPixel = new Random();
            for (int i = 0; i < 200; i++)
            {
                int x = randomPixel.Next(bitMapImage.Width);
                int y = randomPixel.Next(bitMapImage.Height);

                bitMapImage.SetPixel(x, y, Color.FromArgb(randomPixel.Next(0, 255), randomPixel.Next(0, 255), randomPixel.Next(0, 255)));
            }

            //设置图像输出的格式
            context.Response.ContentType = "image/jpeg";

            //保存数据流
            bitMapImage.Save(context.Response.OutputStream, ImageFormat.Jpeg);

            //释放占用的资源
            graphicImage.Dispose();
            bitMapImage.Dispose();

        }

生成中文验证码也可以，根据汉字编码来生成，这里就不发了，本文是自定义的一些简单的文字