class Check_Code

     {

         /// <summary>

         /// 生成随机验证码数字+字母

         /// </summary>

         /// <param name="codelen">验证码长度</param>

         /// <returns>返回验证码</returns>

         public static string MakeCode(int codelen)

         {

             if (codelen < )

             {

                 return string.Empty;

             }

             int number;

             StringBuilder strCheckCode = new StringBuilder();

             Random random = new Random();

             for (int index = ; index < codelen; index++)

             {

                 number = random.Next();

                 if (number %  == )

                 {

                     strCheckCode.Append((char)('' + (char)(number % )));//生成随机数字

                 }

                 else

                 {

                     strCheckCode.Append((char)('A' + (char)(number % )));//生成随机字母

                 }

             }

             return strCheckCode.ToString();

         }

         public static MemoryStream CheckCodeImage(string CheckCode)

         {

             if (string.IsNullOrEmpty(CheckCode))

             {

                 return null;

             }

             Bitmap image = new Bitmap((int)Math.Ceiling((CheckCode.Length * 12.5)), );

             Graphics graphic = Graphics.FromImage(image);//创建一个验证码图片

             try

             {

                 Random random = new Random();

                 graphic.Clear(Color.White);

                 int x1 = , y1 = , x2 = , y2 = ;

                 for (int index = ; index < ; index++)

                 {

                     x1 = random.Next(image.Width);

                     x2 = random.Next(image.Width);

                     y1 = random.Next(image.Height);

                     y2 = random.Next(image.Height);

                     graphic.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);

                 }

                 Font font = new Font("Arial", , (FontStyle.Bold | FontStyle.Italic));//Font设置字体，字号，字形

                 //设置图形渐变色的起始颜色与终止颜色，渐变角度

                 LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(, , image.Width, image.Height), Color.Red, Color.DarkRed, 1.2f, true);

                 graphic.DrawString(CheckCode, font, brush, , );

                 int X = ; int Y = ;

                 //绘制图片的前景噪点

                 for (int i = ; i < ; i++)

                 {

                     X = random.Next(image.Width);

                     Y = random.Next(image.Height);

                     image.SetPixel(X, Y, Color.FromArgb(random.Next()));

                 }

                 //画图片的边框线

                 graphic.DrawRectangle(new Pen(Color.Silver), , , image.Width - , image.Height - );

                 //将图片保存为stream流返回

                 MemoryStream ms = new MemoryStream();

                 image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);

                 return ms;

             }

             finally

             {

                 graphic.Dispose();

                 image.Dispose();

             }

         }

     }