Add Captcha to BlogEngine.Net to kill SPAM comments
This is English version.
The Captcha support ajax.
(0) Modified web.config. Change EnableSessionState="True" in the page section.
(1) Add a new file to the site root directory. The file is named Image.aspx and the code file is Image.aspx.cs.
This is the code.
Image.aspx
01.<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Image.aspx.cs" Inherits="Image" %>
Image.aspx.cs
01.using System;
02.using System.Data;
03.using System.Configuration;
04.using System.Collections;
05.using System.Web;
06.using System.Web.Security;
07.using System.Web.UI;
08.using System.Web.UI.WebControls;
09.using System.Web.UI.WebControls.WebParts;
10.using System.Web.UI.HtmlControls;
11.using System.Drawing;
12.using System.Drawing.Drawing2D;
13.public partial class Image : System.Web.UI.Page
14.{
15. protected void Page_Load(object sender, EventArgs e)
16. {
17. CreateCheckCodeImage(GenCode(4));
18. }
19.
20. private string GenCode(int num)
21. {
22. string[] source ={ "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" };
23. string code = "";
24. Random rd = new Random();
25. int i;
26. for (i = 0; i < num; i++)
27. {
28. code += source[rd.Next(0, source.Length)];
29. }
30. return code;
31.
32. }
33.
34. private void CreateCheckCodeImage(string checkCode)
35. {
36. if (checkCode.Trim() == "" || checkCode == null)
37. return;
38. Session["AlphaCaptchaCode"] = checkCode;
39. System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)(checkCode.Length * 19), 22);
40. Graphics g = Graphics.FromImage(image);
41. try
42. {
43.
44. Random random = new Random();
45.
46. g.Clear(Color.White);
47.
48. int i;
49. for (i = 0; i < 25; i++)
50. {
51. int x1 = random.Next(image.Width);
52. int x2 = random.Next(image.Width);
53. int y1 = random.Next(image.Height);
54. int y2 = random.Next(image.Height);
55. g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
56. }
57.
58. Font font = new System.Drawing.Font("Arial", 14, (System.Drawing.FontStyle.Bold));
59. System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2F, true);
60. g.DrawString(checkCode, font, brush, 4, 1);
61.
62. g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
63. System.IO.MemoryStream ms = new System.IO.MemoryStream();
64. image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
65. Response.ClearContent();
66. Response.ContentType = "image/jpg";
67. Response.BinaryWrite(ms.ToArray());
68.
69. }
70. catch
71. {
72. g.Dispose();
73. image.Dispose();
74. }
75.
76. }
77.}
(2) Modify the CommentView.ascx
(2.1) On the top of the line’<span class="bbcode" title="BBCode tags"><%=BBCodes() %></span>’.Add the code of below.
ATTENCION: in src="/Image.aspx" you need use absolute link, src="http://blog.ambarreira.com/Image.aspx"
01.<label for="<%=txtCaptcha.ClientID %>">Captcha*</label>
02. <img src="/Image.aspx" alt="Click to change captcha" style="width: 82px; height: 23px" onclick="this.src=RefreshCaptcha(this.src)" />
03. <asp:TextBox runat="Server" ID="txtCaptcha" TabIndex="4" MaxLength="4" Width="60px" onblur="DoCheckCaptcha()"/><span id="CaptchaMsg"></span><asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server" ControlToValidate="txtCaptcha" ErrorMessage="<%$Resources:labels, required %>" Display="dynamic" ValidationGroup="AddComment" /><br />
(2.2) Add Checker to the button Save. Change the save button code to this:(This is IMPORTANT)
01.<input type="button" id="btnSaveAjax" value="<%=Resources.labels.saveComment %>" onclick="if(Page_ClientValidate('AddComment')&&checkCaptchaResult){AddComment()}" tabindex="7" />
(2.3) On the top of the line’<asp:label runat="server" id="lbCommentsDisabled" visible="false"><%=Resources.labels.commentsAreClosed %></asp:label>’,Add the code of below.
01.<script type="text/javascript">
02.
03. function DoCheckCaptcha() {
04. var code = document.getElementById("<%=txtCaptcha.ClientID %>").value;
05. checkCaptcha(code);
06. }
07. var checkCaptchaResult=false;
08. function ReceiveServerData(CheckResult) {
09. document.getElementById("CaptchaMsg").innerHTML = "";
10. if (CheckResult == 1) {
11. checkCaptchaResult = true;
12. document.getElementById("CaptchaMsg").innerHTML = "<font color=green>Captcha OK</font>";
13. }
14. else if (CheckResult == -1) {
15. checkCaptchaResult = false;
16. //document.getElementById("CaptchaMsg").innerHTML = "<font color=red>Captcha Error</font>";
17. }
18. else {
19. checkCaptchaResult = false;
20. document.getElementById("CaptchaMsg").innerHTML = "<font color=red>Captcha Error</font>";
21. }
22. }
23. function RefreshCaptcha(url) {
24. if (url.toString().indexOf("?",0) > 0) {
25. url = url.toString().substring(0, url.toString().indexOf("?", 0)) + "?" + new Date().toUTCString();
26. }
27. else{
28. url = url.toString() + "?" + new Date().toUTCString();
29. }
30. return url;
31.
32. }
33. </script>
(3) Modify the file named CommentView.ascx.cs
(3.1) In the function RaiseCallbackEvent,Add the below on the top of the function.
01.if (eventArgument.Length < 1)
02. {
03. _Callback = "-1";
04. return;
05. }
06. if (eventArgument.LastIndexOf("-|-") < 0)
07. {
08. string img = Session["AlphaCaptchaCode"].ToString().ToLower(); ;
09. if (eventArgument.ToLower().Equals(img))
10. {
11. _Callback = "1";
12. }
13. else
14. {
15. _Callback = "0";
16. }
17. return;
18. }
(3.2) In the function Page_Load,Add the below code on the bottom of the line’//InititializeCaptcha();’.
01.string cbReference = Page.ClientScript.GetCallbackEventReference(this, "CheckResult", "ReceiveServerData", "");
02.string callbackScript = "function checkCaptcha(CheckResult){" + cbReference + ";}";
03.Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "checkCaptcha", callbackScript, true);
That's it!!! 
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