验证码

20160204 简单加减乘除验证码

UI

前台UI:
        <div class="row bg-info">
         <form action="Login.ashx" method="post">
            <div>
              <img style="80px;height:30px;" src="getpic.ashx"/>
                    </div>
            <div>
                <input type="text" name="pic" /><input type="submit" value="提交" />
            </div>
              </form>
         </div>
后台代码验证:
        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/html";

            if (context.Request["pic"] != null)
            {
                if (context.Request["pic"] == context.Session["pic"].ToString())
                    context.Response.Write("ok");
                else
                    context.Response.Write("no");
            }

        }

类库：

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "image/jpeg";
            //1. creat bitmap
            using (Image image = new Bitmap(80, 30))
            {
                //2. creat string
                Graphics g = Graphics.FromImage(image);
                //3. start draw string
                g.DrawString(GetString(), new Font("幼圆", 10), Brushes.Yellow, new Point(10, 10));
                //4. list pic
                image.Save(context.Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg);
            }
        }
        private string GetString()
        {
            Random rd = new Random();
            int N1 = rd.Next(10);
            int N2 = rd.Next(10);
            int com = rd.Next(3);// 运算符，operator
            int sum = 0 ;
            string str = "";

            switch (com) {
                case 0:sum = N1 + N2; str = N1 + " + " + N2 + " = "; break;
                case 1:sum = N1 - N2; str = N1 + " - " + N2 + " = "; break;
                case 2:sum = N1 * N2; str = N1 + " × " + N2 + " = "; break;
                default:str = "error";break;
            }
           HttpContext.Current.Session.Add("pic", sum);//生成一个名为session的值
            return str;
        }