ASP.NET 实现验证码以及刷新验证码的小例子

实现代码

/// <summary>
    /// 生成验证码图片，保存session名称verificationcode
    /// </summary>
    public static void createverificationcode()
    {
        int number;
        string checkcode = string.empty;

        //随机数种子
        random randoms = new random();

        for (int i = 0; i < 4; i++) //校验码长度为4
        {
            //随机的整数
            number = randoms.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
            number = number % 36;
            if (number < 10)
            {
                number += 48;
            }
            else
            {
                number += 55;
            }
            checkcode += ((char)number).tostring();
        }

        //在session中保存校验码
        system.web.httpcontext.current.session["verificationcode"] = checkcode;

        //若校验码为空，则直接返回
        if (checkcode == null || checkcode.trim() == string.empty)
        {
            return;
        }
        //根据校验码的长度确定输出图片的长度
        system.drawing.bitmap image = new system.drawing.bitmap(55, 20);//(int)math.ceiling(convert.todouble(checkcode.length * 15))
        //创建graphics对象
        graphics g = graphics.fromimage(image);
        try
        {
            //生成随机数种子
            random random = new random();
            //清空图片背景色
            g.clear(color.white);
            //画图片的背景噪音线 10条
            //---------------------------------------------------
            for (int i = 0; i < 10; i++)
            {
                //噪音线起点坐标(x1,y1),终点坐标(x2,y2)
                int x1 = random.next(image.width);
                int x2 = random.next(image.width);
                int y1 = random.next(image.height);
                int y2 = random.next(image.height);

                //用银色画出噪音线
                g.drawline(new pen(color.silver), x1, y1, x2, y2);
            }
            //---------------------------------------------------
            //brush b = brushes.silver;
            //g.fillrectangle(b, 0, 0, image.width, image.height);
            //---------------------以上两种任选其一------------------------------
            //输出图片中校验码的字体: 12号arial,粗斜体
            font font = new font("arial", 12, (fontstyle.bold | fontstyle.italic));

            //线性渐变画刷
            lineargradientbrush brush = new lineargradientbrush(new rectangle(0, 0, image.width, image.height), color.blue, color.purple, 1.2f, true);
            g.drawstring(checkcode, font, brush, 2, 2);

            //画图片的前景噪音点 50个
            for (int i = 0; i < 50; 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.peru), 0, 0, image.width - 1, image.height - 1);

            //创建内存流用于输出图片
            using (memorystream ms = new memorystream())
            {
                //图片格式指定为png
                image.save(ms, imageformat.jpeg);
                //清除缓冲区流中的所有输出
                system.web.httpcontext.current.response.clearcontent();
                //输出流的http mime类型设置为"image/png"
                system.web.httpcontext.current.response.contenttype = "image/jpeg";
                //输出图片的二进制流
                system.web.httpcontext.current.response.binarywrite(ms.toarray());
            }
        }
        finally
        {
            //释放bitmap对象和graphics对象
            g.dispose();
            image.dispose();
        }
    }

创建一个aspx页面

 <%@ page language="c#" autoeventwireup="true" codefile="authcode.aspx.cs" inherits="authcode" %>

 <%help.createverificationcode(); %>

添加html代码,引用

 <div class="positionr">
     <label>验证码：</label>
     <span class="style1"> *</span>
     <input type="text" class="yanzm" runat="server" reg="^.+$" id="txtauthcode" tip="请输入验证码!" />
     <img class="yanzm_img" src="authcode.aspx" alt="" id="imgauthcode" />
 </div>

如何实现刷新?

     <script type="text/javascript">
         $("#imgauthcode").click(function () {
             $(this).attr("src", "authcode.aspx?code=" + (new date()).gettime());
         });
     </script>

效果图

实例下载