Exampl to create autogenerated code verification

Create a page with name “Captcha.aspx”

   1: IMG height="30" alt="" src=BuildCaptcha.aspx width="80">

   2: asp:TextBox runat="Server" ID="txtCaptcha">

   3: <asp:Button runat="Server" ID="btnSubmit" 

   4:            OnClick="btnSubmit_Click" 

   5:            Text="Submit" />

   6:  

   7: 3. On “btnSubmit_Click” place the following code

   8:  

   9: if (Page.IsValid && (txtCaptcha.Text.ToString() == 

  10:      Session["RandomStr"].ToString()))

  11: {

  12:   Response.Write("Code verification Successful");

  13: }

  14: else

  15: {

  16:   Response.Write( "Please enter info correctly");

  17: }

Create one more page with BuildCaptcha.aspx

   1: Bitmap objBMP = new Bitmap(60, 20);

   2: Graphics objGraphics = Graphics.FromImage(objBMP);

   3: objGraphics.Clear(Color.Wheat);

   4: objGraphics.TextRenderingHint = TextRenderingHint.AntiAlias;

   5:  

   6:  

   7: //' Configure font to use for text

   8: Font objFont = new Font("Arial", 8, FontStyle.Italic);

   9: string randomStr = "";

  10: char[] myArray = new char[5];

  11: int x;

  12:  

  13: //That is to create the random # and add it to our string

  14: Random autoRand = new Random();

  15: for (x = 0; x < 5; x++)

  16: {

  17:   myArray[x] = System.Convert.ToChar(autoRand.Next(65,90));

  18:   randomStr += (myArray[x].ToString());

  19: }

  20:  

  21: //This is to add the string to session, to be compared later

  22: Session.Add("RandomStr", randomStr);

  23:  

  24: //' Write out the text

  25: objGraphics.DrawString(randomStr, objFont, Brushes.Red, 3, 3);

  26:  

  27: //' Set the content type and return the image

  28: Response.ContentType = "image/GIF";

  29: objBMP.Save(Response.OutputStream, ImageFormat.Gif);

  30: objFont.Dispose();

  31: objGraphics.Dispose();

  32: objBMP.Dispose();