ASP.NET生成图片验证码

时间：12-18来源：作者：点击数：33

今天开始做一个新项目，包含完整的注册登陆流程，在登陆时需要输入验证码防止暴力破解。

制作思路是这样的：

准备使用handler一般处理程序来写，先随机从0-9和A-Z里随机取4个数字，将内容保存在Session中供验证时使用。然后使用Bitmap和Graphics画图，最后以image/png类型输出流。

具体代码如下：

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Web;
using System.Web.SessionState;

namespace MyCms.Handler
{
    /// <summary>
    /// VerificationCode 的摘要说明
    /// </summary>
    public class VerificationCode : IHttpHandler, IRequiresSessionState
    {

        public void ProcessRequest(HttpContext context)
        {
            System.Random rand = new Random();
            int len = 4; //rand.Next(4, 6);
            char[] chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
            System.Text.StringBuilder myStr = new System.Text.StringBuilder();
            for (int iCount = 0; iCount < len; iCount++)
            {
                myStr.Append(chars[rand.Next(chars.Length)]);
            }
            string verificationCode = myStr.ToString();
            context.Session["VerificationCode"] = verificationCode;
            Size ImageSize = Size.Empty;
            using (Bitmap bmp = new Bitmap(121, 40)) {
                using (Graphics g = Graphics.FromImage(bmp)) {
                    SolidBrush brush = new SolidBrush(Color.FromArgb(79, 137, 205));
                    g.Clear(Color.FromArgb(197,227,240));
                    g.DrawString(verificationCode, new Font("MS Sans Serif", 26,FontStyle.Strikeout,GraphicsUnit.Pixel), brush, new PointF(18, 6));
                }
                using (System.IO.MemoryStream ms = new System.IO.MemoryStream()) {
                    bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png);
                    context.Response.ContentType = "image/png";
                    ms.WriteTo(context.Response.OutputStream);

                }
            }
            
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}