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Monday, August 04, 2014

How To Create your own captcha image generator in asp.net using c#.net


The below example will generate a captcha code with numbers and alphabets (small and capital letters). You can change the variable  “combination” value according to your requirement. 

 Create two pages Captcha_image.aspx and Registration.aspx

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

<!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>


Captcha_image.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;
using System.Data.SqlClient;
using System.Text;

public partial class Captcha_image : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["captcha"]!= null)
        {
            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.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Data.SqlClient;
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 = "Captcha_image.aspx?" + DateTime.Now.Ticks.ToString();
        }
        catch
        {

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

}

RESULT

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