In this article going to explain how to create
CAPTCHA
in asp.net c#.
Before creating the captcha first we want to know why we using captcha?
Captcha code ids kind of image is used to validate client browser window really has a human typing into it or not Or simply say captcha is only be read by human not by robots.( Robots ia a kind of program that automativally submit the data to the website) and when we want to prevent it we use the captcha.
Now Lets move with creating captcha in asp.net c#
Firstly Create a "GenerateCaptcha.aspx" page
code of GenerateCaptcha.aspx"
Before creating the captcha first we want to know why we using captcha?
Captcha code ids kind of image is used to validate client browser window really has a human typing into it or not Or simply say captcha is only be read by human not by robots.( Robots ia a kind of program that automativally submit the data to the website) and when we want to prevent it we use the captcha.
Now Lets move with creating captcha in asp.net c#
Firstly Create a "GenerateCaptcha.aspx" page
code of 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>
|
code of 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("Segoe
UI", 15, FontStyle.Strikeout),
Brushes.Red, rectf);
g.DrawRectangle(new Pen(Color.Bisque), 1, 1, width - 2, height - 2);
g.Flush();
Response.ContentType =
"image/jpeg";
bmp.Save(Response.OutputStream, ImageFormat.Jpeg);
g.Dispose();
bmp.Dispose();
}
}
|
Now Create another Default.aspx page
<%@
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></title>
</head>
<body>
<form
id="form1"
runat="server">
<div>
<asp:Panel
ID="pnlCheckCaptcha"
runat="server"
GroupingText="<b>Check
Captcha"></b> <table>
<tr>
<td>Write
Catcha Here</td>
<td><asp:TextBox
ID="txtCaptcha"
runat="server"></asp:TextBox></td>
</tr>
<tr>
<td><asp:Image
ID="imgCaptcha"
runat="server"
/></td>
<td>
<asp:Button
ID="btnRefresh"
runat="server"
Text="Refresh"
OnClick="btnRefresh_Click"
/>
</td>
</tr>
<tr>
<td
colspan="2"
align="center"><asp:Button
ID="btnchekcatcha"
runat="server"
Text="Check"
onclick="btnchekcatcha_Click"/>
<asp:Label
ID="lblmsg"
runat="server"
ForeColor="Red"></asp:Label>
</td>
</tr>
</table>
</asp:Panel>
</div>
</form>
</body>
</html>
|
Default.aspx.cs page 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.Imaging;
using
System.Text;
public
partial class
_Default : System.Web.UI.Page
{
protected void Page_Load(object
sender, EventArgs e)
{
try
{
if (!IsPostBack)
{
GetCapctha();
}
}
catch (Exception ex)
{
lblmsg.Text =
ex.Message.ToString();
}
}
void
GetCapctha()
{
try
{
Random random =
new Random();
string combination =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
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)
{
try
{
GetCapctha();
}
catch (Exception ex)
{
lblmsg.Text =
ex.Message.ToString();
}
}
protected void
btnchekcatcha_Click(object sender,
EventArgs e)
{
try
{
if (Session["captcha"].ToString()
!= txtCaptcha.Text)
lblmsg.Text =
"Invalid Captcha Code";
else
lblmsg.Text =
"Valid Captcha Code";
GetCapctha();
}
catch (Exception ex)
{
lblmsg.Text =
ex.Message.ToString();
}
}
}
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Output
