验证码验证

using System;
using System.Drawing;
using System.Web;
using System.Web.Services;
using System.Web.SessionState;

namespace WEB
{
    /// <summary>
    /// $codebehindclassname$ 的摘要说明
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    public class ValidateCode : IHttpHandler, IRequiresSessionState
    {

        public void ProcessRequest(HttpContext context)
        {
            string checkCode = CreateRandomCode(4);
            context.Session["CheckCode"] = checkCode.ToLower();
            CreateImage(checkCode, context);
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

        private static string CreateRandomCode(int codeCount)
        {
            const string allChar = "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";
            string[] allCharArray = allChar.Split(',');
            string randomCode = "";

            var rand = new Random();
            for (int i = 0; i < codeCount; i++)
            {
                int t = rand.Next(35);
                randomCode += allCharArray[t];
            }
            return randomCode;
        }

        private static void CreateImage(string checkCode, HttpContext context)
        {
            var iwidth = checkCode.Length * 13;
            var image = new Bitmap(iwidth, 25);
            Graphics g = Graphics.FromImage(image);
            var f = new Font("Arial", 12, FontStyle.Bold);
            Brush b = new SolidBrush(Color.Black);
            //g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
            g.Clear(Color.White);
            g.DrawString(checkCode, f, b, 3, 3);

            //var blackPen = new Pen(Color.Blue, 0);
            //var rand = new Random();
            //for (int i = 0; i < 5; i++)
            //{
            //    int y = rand.Next(image.Height);
            //    g.DrawLine(blackPen, 0, y, image.Width, y);
            //}
            var rand = new Random();
            for (int i = 0; i < 2; i++)
            {
                g.DrawLine(new Pen(Color.FromArgb(rand.Next(0, 255), rand.Next(0, 255), rand.Next(0, 255))), rand.Next(20) - 10, rand.Next(20) - 10, rand.Next(image.Width) + 10, rand.Next(image.Height) + 10);
            }
            for (int i = 0; i < 2; i++)
            {
                g.DrawArc(new Pen(Color.FromArgb(rand.Next(0, 255), rand.Next(0, 255), rand.Next(0, 255))), rand.Next(20) - 10, rand.Next(20) - 10, rand.Next(image.Width) + 10, rand.Next(image.Height) + 10, rand.Next(-100, 100), rand.Next(-200, 200));
            }
            for (int i = 0; i < 2; i++)
            {
                g.DrawRectangle(
                    new Pen(Color.FromArgb(rand.Next(0, 255), rand.Next(0, 255), rand.Next(0, 255))),
                    rand.Next(2, 128),
                    rand.Next(2, 38),
                    15,
                    15);
            }
            var ms = new System.IO.MemoryStream();
            image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
            context.Response.BinaryWrite(ms.ToArray());
            context.Response.ClearContent();
            context.Response.ContentType = "image/Jpeg";
            context.Response.BinaryWrite(ms.ToArray());
            g.Dispose();
            image.Dispose();
        }
    }
}

 <div class="l w60 z14 lh26">验证码</div>
        <div class="l w56 s4">
          <input id="txtCheckCode" name=keyword accesskey=s maxlength="6" runat="server" />
        </div><div class="l w56 m0_8"><img id="imgCheckCode" src="ValidateCode.ashx" /></div><div class="l w56 lh26"><a href="###" onclick="document.getElementById('imgCheckCode').src='ValidateCode.ashx?code='+Math.random()">看不清</a></div>