.net验证码完整代码

  protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                GenerateCheckCode();
            }
        }

        private void GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;
            System.Random random = new Random();
            for (int i = 0; i < 5; i++)
            {
                number = random.Next();
                if (number % 2 == 0)
                    code = (char)('0' + (char)(number % 10));//当随机数为偶数时去数字
                else
                    code = (char)('A' + (char)(number % 26));//当随机数为奇数时取字符，算法是，用随机数除以26得到一个小于26的数字然后再用A加上这个数字得到一个字符
                checkCode += code.ToString();
            }
            Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));//将产生的字符放入cookie
            Createcode(checkCode);
        }

private void Createcode(string checkCode)
        {
            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);
                Response.ClearContent();
                //response.C;
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }

前台代码：

 <script type="text/javascript">
        var url = '<%= Page.ResolveUrl("~/Code.aspx")%>'; //'" + url + "'?'"  "'
        function getCode() {
            $('#Image1').attr('src', url+ '?' + new Date().getTime().toString(36));
        }
       </script>
    <image id="Image1" src="/Code.aspx"></image>
    <%--<asp:Image ID="Image1" runat="server" ImageUrl="~/Code.aspx" />--%>
    <a href="javascript:void(0);" style="padding: 5 0 5 0;" onclick="getCode()">看不清</a>
    <div>
        <asp:Button ID="btSave" runat="server" Text="保存" onclick="btSave_Click" />
    </div>

前台页面后台：

　　   HttpCookie httpCookie = Request.Cookies["CheckCode"];获取httpcookie值
         string ss = httpCookie.Value;