.net ashx 驗證碼

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);//特別注意，如不加，單擊驗證圖片＇看不清換一張＇，無效果．           
        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裏．            
        //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
        {                 //生成隨機生成器               
            Random random = new Random();

            //清空圖片背景色               
            g.Clear(Color.White);

            //畫圖片的背景噪音線                
            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);

            //畫圖片的前景噪音點                
            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()));
            }

            //畫圖片的邊框線                
            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();
        }

    }
}

 

頁面使用：<img border="0" id="codeIMg" src="UserContorls/ValidCode.ashx" alt="看不清，單擊換一張" onclick="this.src='UserContorls/ValidCode.ashx?abc='+Math.random()"/><br />
        <a href="#" onclick="javascript:document.getElementById('codeIMg').src='UserContorls/ValidateCode.ashx?abc='+Math.random()" onfocus="this.blur()">看不清，換一張</a>

 

這裏 ashx?abc='+Math.random()" 必須，應爲沒有Math.random()，提交的爲同一文件，不會更改，而產生Math.random()，會認爲是不同文件，只起更改提交文件。