登陆验证码

生成字符串的方法

 private string CreateRandomCode(int codeCount)
    {
        string allChar = "0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,W,X,Y,Z";
        string[] allCharArray = allChar.Split(',');
        string randomCode = "";
        int temp = -1;

        Random rand = new Random();
        for (int i = 0; i < codeCount; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * ((int)DateTime.Now.Ticks));
            }
            int t = rand.Next(35);
            if (temp == t)
            {
                return CreateRandomCode(codeCount);
            }
            temp = t;
            randomCode += allCharArray[t];
        }
        return randomCode;
    }

把字符串变成一个图片

 private void CreateImage(string checkCode)
    {
        int iwidth = (int)(checkCode.Length * 11.5);
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 20);
        Graphics g = Graphics.FromImage(image);
        Font f = new System.Drawing.Font("Arial", 10, System.Drawing.FontStyle.Bold);
        Brush b = new System.Drawing.SolidBrush(Color.White);
        //g.FillRectangle(new System.Drawing.SolidBrush(Color.Blue),0,0,image.Width, image.Height);
        g.Clear(Color.Blue);
        g.DrawString(checkCode, f, b, 3, 3);

        Pen blackPen = new Pen(Color.Black, 0);
        Random rand = new Random();
        for (int i = 0; i < 5; i++)
        {
            int y = rand.Next(image.Height);
            g.DrawLine(blackPen, 0, y, image.Width, y);
        }

        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
        Response.ClearContent();
        Response.ContentType = "image/Jpeg";
        Response.BinaryWrite(ms.ToArray());
        g.Dispose();
        image.Dispose();
    }

窗体加载时把字符串放到session中，调用生成图片的方法

protected void Page_Load(object sender, EventArgs e)
    {
        string checkCode = CreateRandomCode(4);
        Session["CheckCode"] = checkCode;
        CreateImage(checkCode);
    }

 

注册页面里价格时间戳

<script language="javascript" type="text/javascript">
        function getimgcode() {
            var num = Math.ceil(Math.random() * 100);       
            var getimagecode = document.getElementById("getcode");
            getimagecode.src = "Captcha.aspx?CheckCode="+num;
        }
</script>

引入页面

  <p>
        <a href="javascript:getimgcode()">看不清楚,再换一张</a>
        <img style ="vertical-align:middle;" id="getcode" src="Captcha.aspx" onclick="getimgcode()" /> 
        </p>

        <p><span>验证码</span><asp:TextBox ID="txtValidator" runat="server" CssClass="UserEmail" ></asp:TextBox><asp:RequiredFieldValidator
                ID="REVValidator" runat="server" ErrorMessage="验证码不正确" ControlToValidate="txtValidator"></asp:RequiredFieldValidator>
        <p>

用户注册时验证

if (txtValidator.Text != Session["CheckCode"].ToString())
        {
            Response.Write("<script >function window.onload() {alert('验证码书写错误!');}</script>");       
        }