.net ashx 验证码

using System; using System.Data; using System.Web; using System.Collections; using System.Web.Services; using System.Web.Services.Protocols; using System.Drawing;

public class ValidateCode : IHttpHandler{

    public void ProcessRequest(HttpContext context)    {        context.Response.Cache.SetCacheability(HttpCacheability.NoCache);//特别注意，如不加，单击验证图片＇看不清换一张＇，无效果．                    this.CreateCheckCodeImage(GenerateCheckCode(context), context);    }

    public bool IsReusable    {        get        {            return false;        }    }    private string GenerateCheckCode(HttpContext context)    {        int number;        char code;        string checkCode = String.Empty;        System.Random random = new Random();        for (int i = 0; i < 6; i++)        {            number = random.Next();            if (number % 2 == 0)                code = (char)('0' + (char)(number % 10));            else if (number % 3 == 0)                code = (char)('A' + (char)(number % 26));            else                code = (char)('a' + (char)(number % 26));            checkCode += code.ToString();        }        context.Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));//也可以存到Seesion里．                     //context.Session["CheckCode"] = checkCode;                                return checkCode;    }

    private void CreateCheckCodeImage(string checkCode, HttpContext context)    {        if (checkCode == null || checkCode.Trim() == String.Empty)            return;        System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);        Graphics g = Graphics.FromImage(image);        try        {                 //生成随机生成器                            Random random = new Random();

            //清空图片背景色                            g.Clear(Color.White);

            //画图片的背景噪音线                             for (int i = 0; i < 25; i++)            {                int x1 = random.Next(image.Width);                int x2 = random.Next(image.Width);                int y1 = random.Next(image.Height);                int y2 = random.Next(image.Height);                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);            }            Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true); g.DrawString(checkCode, font, brush, 2, 2);

            //画图片的前景噪音点                             for (int i = 0; i < 100; i++)            {                int x = random.Next(image.Width);                int y = random.Next(image.Height);                image.SetPixel(x, y, Color.FromArgb(random.Next()));            }

            //画图片的边框线                             g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

            System.IO.MemoryStream ms = new System.IO.MemoryStream();            image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);            context.Response.ClearContent();            context.Response.ContentType = "image/Gif";            context.Response.BinaryWrite(ms.ToArray());        }        finally        {            g.Dispose();            image.Dispose();        }

    }}

 

页面使用：<img border="0" id="codeIMg" src="UserContorls/ValidCode.ashx" alt="看不清，单击换一张" οnclick="this.src='UserContorls/ValidCode.ashx?abc='+Math.random()"/><br />        <a href="#" οnclick="javascript:document.getElementById('codeIMg').src='UserContorls/ValidateCode.ashx?abc='+Math.random()" οnfοcus="this.blur()">看不清，换一张</a>

 

这里 ashx?abc='+Math.random()" 必须，应为没有Math.random()，提交的为同一文件，不会更改，而产生Math.random()，会认为是不同文件，只起更改提交文件。