Showing posts with label Random captcha code. Show all posts
Showing posts with label Random captcha code. Show all posts

Monday, July 23, 2018

how to generate random captcha code for registration form | Sradha WEbCreations

how to generate random captcha code for registration form to avoid robot attack 

 http://sradhawebcreations.com


Create two pages GenerateCaptcha.aspx & Registration.aspx


GenerateCaptcha.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="GenerateCaptcha.aspx.cs"
 Inherits="GenerateCaptcha"%>

<!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></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
   
    </div>
    </form>
</body>
</html>


GenerateCaptcha.aspx.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;

public partial class GenerateCaptcha : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Clear();
        int height = 30;
        int width = 100;
        Bitmap bmp = new Bitmap(width, height);

        RectangleF rectf = new RectangleF(10, 5, 0, 0);

        Graphics g = Graphics.FromImage(bmp);
        g.Clear(Color.White);
        g.SmoothingMode = SmoothingMode.AntiAlias;
        g.InterpolationMode = InterpolationMode.HighQualityBicubic;
        g.PixelOffsetMode = PixelOffsetMode.HighQuality;
        g.DrawString(Session["captcha"].ToString(), new Font("Thaoma", 12, FontStyle.Italic),Brushes.Green, rectf);
        g.DrawRectangle(new Pen(Color.Red), 1, 1, width-2, height-2);
        g.Flush();
        Response.ContentType = "image/jpeg";
        bmp.Save(Response.OutputStream, ImageFormat.Jpeg);
        g.Dispose();
        bmp.Dispose();
    }
}


Registration.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Registration.aspx.cs" Inherits="Registration" %>

<!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></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ScriptManager ID="SM1" runat="server">
        </asp:ScriptManager>
        <table style="border: solid 1px black; padding: 20px; position: relative; top: 50px;"
            align="center">
            <tr>
                <td>
                    Email ID :
                </td>
                <td>
                    <asp:TextBox ID="txtEmailID" runat="server" Width="200px"></asp:TextBox>
                </td>
            </tr>
            <tr>
                <td>
                    Password :
                </td>
                <td>
                    <asp:TextBox ID="txtPassword" runat="server" TextMode="Password" Width="200px">
</asp:TextBox>
                </td>
            </tr>
            <tr>
                <td>
                    Confirm Password :
                </td>
                <td>
                    <asp:TextBox ID="txtConfirmPassword" runat="server" TextMode="Password" 
Width="200px"></asp:TextBox>
                </td>
            </tr>
            <tr>
                <td>
                    Enter Below Code :
                </td>
                <td>
                    <asp:TextBox ID="txtCaptcha" runat="server" Width="200px"></asp:TextBox>
                </td>
            </tr>
            <tr>
                <td>
                </td>
                <td valign="middle">
                    <asp:UpdatePanel ID="UP1" runat="server">
                        <ContentTemplate>
                            <table>
                                <tr>
                                    <td style="height: 50px; width:100px;">
                                        <asp:Image ID="imgCaptcha" runat="server" />
                                    </td>
                                    <td valign="middle">
      <asp:Button ID="btnRefresh" runat="server" Text="Refresh"OnClick="btnRefresh_Click" />
                                    </td>
                                </tr>
                            </table>
                        </ContentTemplate>
                    </asp:UpdatePanel>
                </td>
            </tr>
            <tr>
                <td colspan="2" align="center">
        <asp:Button ID="btnRegiser" runat="server" Text="Register" OnClick="btnRegister_Click"/>
                </td>
            </tr>
        </table>
    </div>
    </form>
</body>
</html>
  
Registration.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;

public partial class Registration : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            FillCapctha();
        }
    }

    void FillCapctha()
    {
        try
        {
            Random random = new Random();
            string combination = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
            StringBuilder captcha = new StringBuilder();
            for (int i = 0; i < 6; i++)
                captcha.Append(combination[random.Next(combination.Length)]);
            Session["captcha"] = captcha.ToString();
            imgCaptcha.ImageUrl = "GenerateCaptcha.aspx?" + DateTime.Now.Ticks.ToString();
        }
        catch
        {

            throw;
        }
    }

    protected void btnRefresh_Click(object sender, EventArgs e)
    {
        FillCapctha();
    }

    protected void btnRegister_Click(object sender, EventArgs e)
    {
        if (Session["captcha"].ToString() != txtCaptcha.Text)
            Response.Write("Invalid Captcha Code");
        else
            Response.Write("Valid Captcha Code");
        FillCapctha();
    }

}

CAPTCHA offers safety and security in a number of ways.
  1. By distinguishing between humans and automated computer programs, 
  2. Protecting Registration Forms in Websites
  3. Making Online Shopping More Secure
  4. Preventing Spam Comments
  5. Want to Avoid CAPTCHAs, Try these Alternatives The Math Puzzle