asp .net c# website form with captcha control

1. Home.aspx

<asp:Label ID=”lblmsg” runat=”server” Font-Bold=”True” ForeColor=”Red” Text=”” />
<br />
Enter code shown below in text box.
<asp:TextBox ID=”txtimgcode” runat=”server” ValidationGroup=”1″ /><br />
<img height=”70″ width=”200″ src=”CImage.aspx” alt=”” />
<br />
<asp:Button ID=”Button1″ runat=”server” Text=”Validate” OnClick=”Button1_Click” />

2. Home.aspx.cs

protected void Button1_Click(object sender, EventArgs e)
{
if (this.txtimgcode.Text == this.Session[“CaptchaImageText”].ToString())
{
lblmsg.Text = “Excellent…….”;
}
else
{
lblmsg.Text = “image code is not valid.”;
}
this.txtimgcode.Text = “”;
}

3. CImage.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
// Create a random code and store it in the Session object.
this.Session[“CaptchaImageText”] = GenerateRandomCode();
// Create a CAPTCHA image using the text stored in the Session object.
RandomImage ci = new RandomImage(this.Session
[“CaptchaImageText”].ToString(), 300, 75);
// Change the response headers to output a JPEG image.
this.Response.Clear();
this.Response.ContentType = “image/jpeg”;
// Write the image to the response stream in JPEG format.
ci.Image.Save(this.Response.OutputStream, ImageFormat.Jpeg);
// Dispose of the CAPTCHA image object.
ci.Dispose();
}

// Function to generate random string with Random class.
private string GenerateRandomCode()
{
Random r = new Random();
string s = “”;
for (int j = 0; j < 5; j++)
{
int i = r.Next(3);
int ch;
switch (i)
{
case 1:
ch = r.Next(0, 9);
s = s + ch.ToString();
break;
case 2:
ch = r.Next(65, 90);
s = s + Convert.ToChar(ch).ToString();
break;
case 3:
ch = r.Next(97, 122);
s = s + Convert.ToChar(ch).ToString();
break;
default:
ch = r.Next(97, 122);
s = s + Convert.ToChar(ch).ToString();
break;
}
r.NextDouble();
r.Next(100, 1999);
}
return s;
}

4. RandomImage.cs Library

//Extra name space
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Drawing.Text;
using System;
public class RandomImage
{
//Default Constructor
public RandomImage() { }
//property
public string Text
{
get { return this.text; }
}
public Bitmap Image
{
get { return this.image; }
}
public int Width
{
get { return this.width; }
}
public int Height
{
get { return this.height; }
}
//Private variable
private string text;
private int width;
private int height;
private Bitmap image;
private Random random = new Random();
//Methods declaration
public RandomImage(string s, int width, int height)
{
this.text = s;
this.SetDimensions(width, height);
this.GenerateImage();
}
public void Dispose()
{
GC.SuppressFinalize(this);
this.Dispose(true);
}
protected virtual void Dispose(bool disposing)
{
if (disposing)
this.image.Dispose();
}
private void SetDimensions(int width, int height)
{
if (width <= 0)
throw new ArgumentOutOfRangeException(“width”, width,
“Argument out of range, must be greater than zero.”);
if (height <= 0)
throw new ArgumentOutOfRangeException(“height”, height,
“Argument out of range, must be greater than zero.”);
this.width = width;
this.height = height;
}
private void GenerateImage()
{
Bitmap bitmap = new Bitmap
(this.width, this.height, PixelFormat.Format32bppArgb);
Graphics g = Graphics.FromImage(bitmap);
g.SmoothingMode = SmoothingMode.AntiAlias;
Rectangle rect = new Rectangle(0, 0, this.width, this.height);
HatchBrush hatchBrush = new HatchBrush(HatchStyle.SmallConfetti,
Color.LightGray, Color.White);
g.FillRectangle(hatchBrush, rect);
SizeF size;
float fontSize = rect.Height + 1;
Font font;

do
{
fontSize–;
font = new Font(FontFamily.GenericSansSerif, fontSize, FontStyle.Bold);
size = g.MeasureString(this.text, font);
} while (size.Width > rect.Width);
StringFormat format = new StringFormat();
format.Alignment = StringAlignment.Center;
format.LineAlignment = StringAlignment.Center;
GraphicsPath path = new GraphicsPath();
//path.AddString(this.text, font.FontFamily, (int) font.Style,
//    font.Size, rect, format);
path.AddString(this.text, font.FontFamily, (int)font.Style, 75, rect, format);
float v = 4F;
PointF[] points =
{
new PointF(this.random.Next(rect.Width) / v, this.random.Next(
rect.Height) / v),
new PointF(rect.Width – this.random.Next(rect.Width) / v,
this.random.Next(rect.Height) / v),
new PointF(this.random.Next(rect.Width) / v,
rect.Height – this.random.Next(rect.Height) / v),
new PointF(rect.Width – this.random.Next(rect.Width) / v,
rect.Height – this.random.Next(rect.Height) / v)
};
Matrix matrix = new Matrix();
matrix.Translate(0F, 0F);
path.Warp(points, rect, matrix, WarpMode.Perspective, 0F);
hatchBrush = new HatchBrush(HatchStyle.Percent10, Color.Black, Color.SkyBlue);
g.FillPath(hatchBrush, path);
int m = Math.Max(rect.Width, rect.Height);
for (int i = 0; i < (int)(rect.Width * rect.Height / 30F); i++)
{
int x = this.random.Next(rect.Width);
int y = this.random.Next(rect.Height);
int w = this.random.Next(m / 50);
int h = this.random.Next(m / 50);
g.FillEllipse(hatchBrush, x, y, w, h);
}
font.Dispose();
hatchBrush.Dispose();
g.Dispose();
this.image = bitmap;
}
}

Good Luck…!!!

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