How To Randomly Generate Verification Code

Posted by VISHAL RANE at 14:56 Thursday, 7 July 2011
USING C#
Step 1:
  • Create A New Website.
  • Code For Default.aspx(Source)

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Verification code to prevent auto signup in ASP.NET</title>
    </head>
<body>
    <form id="form1" runat="server">
    <div>
   
    </div>
    </form>
</body>
</html>

Step 2:
  • Code For Default.aspx.cs
  • Namespaces Used

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string checkCode = this.CreateRandomCode(6);
        Session["CheckCode"] = checkCode;
        CreateImage(checkCode);

    }

private void CreateImage(string checkCode)
    {
        System.Drawing.Bitmap image = new System.Drawing.Bitmap(Convert.ToInt32(Math.Ceiling((decimal)(checkCode.Length * 14))), 22);
        Graphics g = Graphics.FromImage(image);


        try
        {

            Random random = new Random();
            g.Clear(Color.AliceBlue);

            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("Roman", 12, System.Drawing.FontStyle.Bold);
            System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.CornflowerBlue, Color.DarkMagenta, 1.2f, true);
            g.DrawString(checkCode, font, new SolidBrush(Color.DarkMagenta), 2, 2);


            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()));
            }

            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.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }

public 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,V,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(36);
            if (temp != -1 && temp == t)
            {
                return CreateRandomCode(codeCount);
            }
            temp = t;
            randomCode += allCharArray[t];
        }
        return randomCode;
    }
}
Finally Screen Will Look Like Follows:
Yahoo Screen                                                                          This Code Output:

 


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