Purvi's Blog: Captcha Code In Asp.Net Using C#

Captcha Code In Asp.Net Using C#

So for this current article first you needed to create a new asp.net application. in this add two aspx file first default.aspx and second one is captchacode.aspx .
In your captchacode.aspx add the below code . This code is used for making the captcha code.

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.Text;
using System.Drawing.Imaging;
using System.IO;
namespace Cappachacode
{
    public partial class captcha : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Random r = new Random();
            //Captcha no
            string captchacode = r.Next(10000, 99999).ToString();
            //Storing captcha no in sessin to validate
            Session["captchacode"] = captchacode;
            Color FontColor = Color.Blue;
            Color BackColor = Color.White;
            //Define fone name
            String FontName = "Arial";
            //Define the font size
            int FontSize = 40;
            //define captcha height
            int Height = 60;
            //Define captcha width
            int Width = 174;
            //Define bit map image width and height
            Bitmap bitmap = new Bitmap(Width, Height);
            Graphics graphics = Graphics.FromImage(bitmap);
            Color color = Color.Gray; ;
            Font font = new Font(FontName, FontSize);
            //define where the text will be displayed in the specified area of the image
            PointF point = new PointF(5.0F, 5.0F);
            //Assigning fone color
            SolidBrush BrushForeColor = new SolidBrush(FontColor);
            //Define captcha background color
            SolidBrush BrushBackColor = new SolidBrush(BackColor);
            Pen BorderPen = new Pen(color);
            Rectangle displayRectangle = new Rectangle(new Point(0, 0), new Size(Width - 1, Height - 1));
            graphics.FillRectangle(BrushBackColor, displayRectangle);
            graphics.DrawRectangle(BorderPen, displayRectangle);

            //Define string format
            StringFormat format1 = new StringFormat(StringFormatFlags.NoClip);
            StringFormat format2 = new StringFormat(format1);
            //Draw text string using the text format
            graphics.DrawString(captchacode, font, Brushes.Red, (RectangleF)displayRectangle, format2);
            Response.ContentType = "image/jpeg";
            //Defining bitmap type
            bitmap.Save(Response.OutputStream, ImageFormat.Jpeg);
        }
    }
}

Here i have stored the random no in session. this session value we will validate with the user entered value.
your .aspx page will look as shown below.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="captcha.aspx.cs" Inherits="Cappachacode.captcha" %>

Now come your default.aspx page . in this page add a text box and a button anda image control.
In this image url will be the the path of the image.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="Cappachacode.WebForm1" %>

<!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">
    <asp:Label ID="lblmessage" runat="server"
        style="color: #FFFFFF; font-weight: 700; background-color: #FF0000"></asp:Label>
    <br />
    <br />
    <asp:TextBox ID="TextBox1" runat="server" Width="200px"></asp:TextBox>
 
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click"
        Text="Validate Captcha" />
    <br />
    <br />
    <asp:Image ID="Image1" runat="server" Height="40px" ImageUrl="captcha.aspx"
        Width="149px" />
    </form>
</body>
</html>

Now generate the button click event of the button and add the below code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace Cappachacode
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            string captchacode=Session["captchacode"].ToString();
            if (captchacode == TextBox1.Text)
            {
                Response.Redirect("WebForm2.aspx");
            }
            else
            {
                lblmessage.Text = "You have entered WRONG captcha code.";
            }
        }

    }
}

now run the application.

captcha code