ashx 验证码

<%@ WebHandler Language="C#" Class="ValidateCode" Debug="true" %>

using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.Web.SessionState;//一般处理程序中如果要使用Session必须实现此命名空间里的接口

/// <summary>
/// 验证码
/// </summary>
public class ValidateCode : IHttpHandler,IRequiresSessionState{
   
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "image/jpeg";
        string vCode = MakeRandomNum();
        context.Session["vcode"] = vCode;
        //创建验证码图片对象
        using (Bitmap img = new Bitmap(80, 30))
        {
            using (Graphics g = Graphics.FromImage(img))
            {
                g.DrawString(vCode, new Font("微软雅黑", 16), Brushes.White, 5, 2);
                img.Save(context.Response.OutputStream, ImageFormat.Jpeg);
            }
        }
    }

    /// <summary>
    /// 生成随机验证码
    /// </summary>
    /// <returns></returns>
    public string MakeRandomNum()
    {
        int codelength = 4;
        int resNum=0;
        string RandomCode = string.Empty;
        Random r = new Random();
        for (int i = 0; i < codelength; i++)
        {
            resNum = r.Next();
            //字符从0~9，A~Z中随机产生，对应的Ascii码分别为48-57，65-90
            resNum = resNum % 36;
            if (resNum < 10)
            {
                resNum += 48;
            }
            else
            {
                resNum += 55;
            }
            RandomCode += ((char)resNum).ToString();
        }
        return RandomCode;
    }

    public bool IsReusable
    {
        get {
            return false;
        }
    }

}