Captcha Control In Asp.net

Captcha Control In Asp.net


Hi Friends,
Here i will explain you how to implement captcha control in asp.net.


ON ASPX  PAGE :-
Paste below Script in your form tag.

<div>
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" 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>
        Enter Captcha:
        <asp:TextBox ID="txtCaptcha" runat="server"></asp:TextBox><br />
        <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" />
        <asp:Label ID="lblmsg" runat="server"></asp:Label>
    </div>

ON CODE BEHIND 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;
using System.Drawing.Imaging;  


protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                FillCaptcha();
            }
        }

        public void FillCaptcha()
        {
            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";
            }
            catch
            {

                throw;
            }
        }

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

        protected void btnSubmit_Click(object sender, EventArgs e)
        {
            if (Session["captcha"].ToString() != txtCaptcha.Text)
            {
                lblmsg.ForeColor = System.Drawing.Color.Red;
                lblmsg.Text = "Enter Valid Captcha Code";
            }
            else
            {
                lblmsg.ForeColor = System.Drawing.Color.Green;
                lblmsg.Text = "Enter code is correct";
            }
            FillCaptcha();
        }


Add one new aspx page GenerateCaptcha.aspx 

On code behind


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

 protected void Page_Load(object sender, EventArgs e)
        {
            Response.Clear();
            int height = 40;
            int width = 110;
            Bitmap bmp = new Bitmap(width, height);
            RectangleF rectf = new RectangleF(12, 6, 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("Cambria", 13, FontStyle.Bold), Brushes.Red, rectf);
            g.DrawRectangle(new Pen(Color.Green), 1, 1, width - 15, height - 10);
            g.Flush();
            Response.ContentType = "image/jpeg";
            bmp.Save(Response.OutputStream, ImageFormat.Jpeg);
            g.Dispose();
            bmp.Dispose();
        }