记录几个字符串转html的帮助类，以防忘记

html的帮助类

  1 /// <summary>
  2 /// Represents a HTML helper
  3 /// </summary>
  4 public partial class HtmlHelper
  5 {
  6     #region Fields
  7     private readonly static Regex paragraphStartRegex = new Regex("<p>", RegexOptions.IgnoreCase);
  8     private readonly static Regex paragraphEndRegex = new Regex("</p>", RegexOptions.IgnoreCase);
  9     //private static Regex ampRegex = new Regex("&(?!(?:#[0-9]{2,4};|[a-z0-9]+;))", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 10 
 11     #endregion
 12 
 13     #region Utilities
 14 
 15     private static string EnsureOnlyAllowedHtml(string text)
 16     {
 17         if (String.IsNullOrEmpty(text))
 18             return string.Empty;
 19 
 20         const string allowedTags = "br,hr,b,i,u,a,div,ol,ul,li,blockquote,img,span,p,em,strong,font,pre,h1,h2,h3,h4,h5,h6,address,cite";
 21 
 22         var m = Regex.Matches(text, "<.*?>", RegexOptions.IgnoreCase);
 23         for (int i = m.Count - 1; i >= 0; i--)
 24         {
 25             string tag = text.Substring(m[i].Index + 1, m[i].Length - 1).Trim().ToLower();
 26 
 27             if (!IsValidTag(tag, allowedTags))
 28             {
 29                 text = text.Remove(m[i].Index, m[i].Length);
 30             }
 31         }
 32 
 33         return text;
 34     }
 35 
 36     private static bool IsValidTag(string tag, string tags)
 37     {
 38         string[] allowedTags = tags.Split(',');
 39         if (tag.IndexOf("javascript") >= 0) return false;
 40         if (tag.IndexOf("vbscript") >= 0) return false;
 41         if (tag.IndexOf("onclick") >= 0) return false;
 42 
 43         var endchars = new [] { ' ', '>', '/', '	' };
 44 
 45         int pos = tag.IndexOfAny(endchars, 1);
 46         if (pos > 0) tag = tag.Substring(0, pos);
 47         if (tag[0] == '/') tag = tag.Substring(1);
 48 
 49         foreach (string aTag in allowedTags)
 50         {
 51             if (tag == aTag) return true;
 52         }
 53 
 54         return false;
 55     }
 56     #endregion
 57 
 58     #region Methods
 59     /// <summary>
 60     /// Formats the text
 61     /// </summary>
 62     /// <param name="text">Text</param>
 63     /// <param name="stripTags">A value indicating whether to strip tags</param>
 64     /// <param name="convertPlainTextToHtml">A value indicating whether HTML is allowed</param>
 65     /// <param name="allowHtml">A value indicating whether HTML is allowed</param>
 66     /// <param name="allowBBCode">A value indicating whether BBCode is allowed</param>
 67     /// <param name="resolveLinks">A value indicating whether to resolve links</param>
 68     /// <param name="addNoFollowTag">A value indicating whether to add "noFollow" tag</param>
 69     /// <returns>Formatted text</returns>
 70     public static string FormatText(string text, bool stripTags,
 71         bool convertPlainTextToHtml, bool allowHtml, 
 72         bool allowBBCode, bool resolveLinks, bool addNoFollowTag)
 73     {
 74 
 75         if (String.IsNullOrEmpty(text))
 76             return string.Empty;
 77 
 78         try
 79         {
 80             if (stripTags)
 81             {
 82                 text = StripTags(text);
 83             }
 84 
 85             text = allowHtml ? EnsureOnlyAllowedHtml(text) : HttpUtility.HtmlEncode(text);
 86 
 87             if (convertPlainTextToHtml)
 88             {
 89                 text = ConvertPlainTextToHtml(text);
 90             }
 91 
 92             if (allowBBCode)
 93             {
 94                 text = BBCodeHelper.FormatText(text, true, true, true, true, true, true, true);
 95             }
 96 
 97             if (resolveLinks)
 98             {
 99                 text = ResolveLinksHelper.FormatText(text);
100             }
101 
102             if (addNoFollowTag)
103             {
104                 //add noFollow tag. not implemented
105             }
106         }
107         catch (Exception exc)
108         {
109             text = string.Format("Text cannot be formatted. Error: {0}", exc.Message);
110         }
111         return text;
112     }
113     
114     /// <summary>
115     /// Strips tags
116     /// </summary>
117     /// <param name="text">Text</param>
118     /// <returns>Formatted text</returns>
119     public static string StripTags(string text)
120     {
121         if (String.IsNullOrEmpty(text))
122             return string.Empty;
123 
124         text = Regex.Replace(text, @"(>)(
|
)*(<)", "><");
125         text = Regex.Replace(text, "(<[^>]*>)([^<]*)", "$2");
126         text = Regex.Replace(text, "(&#x?[0-9]{2,4};|&quot;|&amp;|&nbsp;|&lt;|&gt;|&euro;|&copy;|&reg;|&permil;|&Dagger;|&dagger;|&lsaquo;|&rsaquo;|&bdquo;|&rdquo;|&ldquo;|&sbquo;|&rsquo;|&lsquo;|&mdash;|&ndash;|&rlm;|&lrm;|&zwj;|&zwnj;|&thinsp;|&emsp;|&ensp;|&tilde;|&circ;|&Yuml;|&scaron;|&Scaron;)", "@");
127 
128         return text;
129     }
130 
131     /// <summary>
132     /// replace anchor text (remove a tag from the following url <a href="http://example.com">Name</a> and output only the string "Name")
133     /// </summary>
134     /// <param name="text">Text</param>
135     /// <returns>Text</returns>
136     public static string ReplaceAnchorTags(string text)
137     {
138         if (String.IsNullOrEmpty(text))
139             return string.Empty;
140 
141         text = Regex.Replace(text, @"<a[^>]+>([^<]*(?:(?!</a)<[^<]*)*)</a>", "$1", RegexOptions.IgnoreCase);
142         return text;
143     }
144 
145     /// <summary>
146     /// Converts plain text to HTML
147     /// </summary>
148     /// <param name="text">Text</param>
149     /// <returns>Formatted text</returns>
150     public static string ConvertPlainTextToHtml(string text)
151     {
152         if (String.IsNullOrEmpty(text))
153             return string.Empty;
154 
155         text = text.Replace("
", "<br />");
156         text = text.Replace("
", "<br />");
157         text = text.Replace("
", "<br />");
158         text = text.Replace("	", "&nbsp;&nbsp;");
159         text = text.Replace("  ", "&nbsp;&nbsp;");
160 
161         return text;
162     }
163     
164     /// <summary>
165     /// Converts HTML to plain text
166     /// </summary>
167     /// <param name="text">Text</param>
168     /// <param name="decode">A value indicating whether to decode text</param>
169     /// <param name="replaceAnchorTags">A value indicating whether to replace anchor text (remove a tag from the following url <a href="http://example.com">Name</a> and output only the string "Name")</param>
170     /// <returns>Formatted text</returns>
171     public static string ConvertHtmlToPlainText(string text,
172         bool decode = false, bool replaceAnchorTags = false)
173     {
174         if (String.IsNullOrEmpty(text))
175             return string.Empty;
176 
177         if (decode)
178             text = HttpUtility.HtmlDecode(text);
179 
180         text = text.Replace("<br>", "
");
181         text = text.Replace("<br >", "
");
182         text = text.Replace("<br />", "
");
183         text = text.Replace("&nbsp;&nbsp;", "	");
184         text = text.Replace("&nbsp;&nbsp;", "  ");
185 
186         if (replaceAnchorTags)
187             text = ReplaceAnchorTags(text);
188 
189         return text;
190     }
191 
192     /// <summary>
193     /// Converts text to paragraph
194     /// </summary>
195     /// <param name="text">Text</param>
196     /// <returns>Formatted text</returns>
197     public static string ConvertPlainTextToParagraph(string text)
198     {
199         if (String.IsNullOrEmpty(text))
200             return string.Empty;
201 
202         text = paragraphStartRegex.Replace(text, string.Empty);//把c#中的换行转换成html中的换行，源字符串中如果存在标签<p></p>，那么先转成c#中的换行符，最后把所有的c#换行符转换成<p></p>标签的字符串
203         text = paragraphEndRegex.Replace(text, "
");
204         text = text.Replace("
", "
").Replace("
", "
");
205         text = text + "

";
206         text = text.Replace("

", "
");
207         var strArray = text.Split(new [] { '
' });
208         var builder = new StringBuilder();
209         foreach (string str in strArray)
210         {
211             if ((str != null) && (str.Trim().Length > 0))
212             {
213                 builder.AppendFormat("<p>{0}</p>
", str);
214             }
215         }
216         return builder.ToString();
217     }
218     #endregion
219 }

锚标签的帮助类

  1 /// <summary>
  2 /// Represents a ResolveLinks helper
  3 /// </summary>
  4 public partial class ResolveLinksHelper
  5 {
  6     #region Fields
  7     /// <summary>
  8     /// The regular expression used to parse links.
  9     /// </summary>
 10     private static readonly Regex regex = new Regex("((http://|https://|www\.)([A-Z0-9.\-]{1,})\.[0-9A-Z?;~&\(\)#,=\-_\./\+]{2,})", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 11     private const string link = "<a href="{0}{1}" rel="nofollow">{2}</a>";
 12     private const int MAX_LENGTH = 50;
 13     #endregion
 14 
 15     #region Utilities
 16 
 17     /// <summary>
 18     /// Shortens any absolute URL to a specified maximum length
 19     /// </summary>
 20     private static string ShortenUrl(string url, int max)
 21     {
 22         if (url.Length <= max)
 23             return url;
 24 
 25         // Remove the protocal
 26         int startIndex = url.IndexOf("://");
 27         if (startIndex > -1)
 28             url = url.Substring(startIndex + 3);
 29 
 30         if (url.Length <= max)
 31             return url;
 32 
 33         // Compress folder structure
 34         int firstIndex = url.IndexOf("/") + 1;
 35         int lastIndex = url.LastIndexOf("/");
 36         if (firstIndex < lastIndex)
 37         {
 38             url = url.Remove(firstIndex, lastIndex - firstIndex);
 39             url = url.Insert(firstIndex, "...");
 40         }
 41 
 42         if (url.Length <= max)
 43             return url;
 44 
 45         // Remove URL parameters
 46         int queryIndex = url.IndexOf("?");
 47         if (queryIndex > -1)
 48             url = url.Substring(0, queryIndex);
 49 
 50         if (url.Length <= max)
 51             return url;
 52 
 53         // Remove URL fragment
 54         int fragmentIndex = url.IndexOf("#");
 55         if (fragmentIndex > -1)
 56             url = url.Substring(0, fragmentIndex);
 57 
 58         if (url.Length <= max)
 59             return url;
 60 
 61         // Compress page
 62         firstIndex = url.LastIndexOf("/") + 1;
 63         lastIndex = url.LastIndexOf(".");
 64         if (lastIndex - firstIndex > 10)
 65         {
 66             string page = url.Substring(firstIndex, lastIndex - firstIndex);
 67             int length = url.Length - max + 3;
 68             if (page.Length > length)
 69                 url = url.Replace(page, "..." + page.Substring(length));
 70         }
 71 
 72         return url;
 73     }
 74     #endregion
 75 
 76     #region Methods
 77     /// <summary>
 78     /// Formats the text
 79     /// </summary>
 80     /// <param name="text">Text</param>
 81     /// <returns>Formatted text</returns>
 82     public static string FormatText(string text)
 83     {
 84         if (String.IsNullOrEmpty(text))
 85             return string.Empty;
 86 
 87         var info = CultureInfo.InvariantCulture;
 88         foreach (Match match in regex.Matches(text))
 89         {
 90             if (!match.Value.Contains("://"))
 91             {
 92                 text = text.Replace(match.Value, string.Format(info, link, "http://", match.Value, ShortenUrl(match.Value, MAX_LENGTH)));
 93             }
 94             else
 95             {
 96                 text = text.Replace(match.Value, string.Format(info, link, string.Empty, match.Value, ShortenUrl(match.Value, MAX_LENGTH)));
 97             }
 98         }
 99 
100         return text;
101     }
102     #endregion
103 }

bbcode的帮助类

  1 /// <summary>
  2 /// Represents a BBCode helper
  3 /// </summary>
  4 public partial class BBCodeHelper
  5 {
  6     #region Fields
  7     private static readonly Regex regexBold = new Regex(@"[b](.+?)[/b]", RegexOptions.Compiled | RegexOptions.IgnoreCase);
  8     private static readonly Regex regexItalic = new Regex(@"[i](.+?)[/i]", RegexOptions.Compiled | RegexOptions.IgnoreCase);
  9     private static readonly Regex regexUnderLine = new Regex(@"[u](.+?)[/u]", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 10     private static readonly Regex regexUrl1 = new Regex(@"[url=([^]]+)]([^]]+)[/url]", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 11     private static readonly Regex regexUrl2 = new Regex(@"[url](.+?)[/url]", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 12     private static readonly Regex regexQuote = new Regex(@"[quote=(.+?)](.+?)[/quote]", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 13     private static readonly Regex regexImg = new Regex(@"[img](.+?)[/img]", RegexOptions.Compiled | RegexOptions.IgnoreCase);
 14 
 15     #endregion
 16 
 17     #region Methods
 18     /// <summary>
 19     /// Formats the text
 20     /// </summary>
 21     /// <param name="text">Text</param>
 22     /// <param name="replaceBold">A value indicating whether to replace Bold</param>
 23     /// <param name="replaceItalic">A value indicating whether to replace Italic</param>
 24     /// <param name="replaceUnderline">A value indicating whether to replace Underline</param>
 25     /// <param name="replaceUrl">A value indicating whether to replace URL</param>
 26     /// <param name="replaceCode">A value indicating whether to replace Code</param>
 27     /// <param name="replaceQuote">A value indicating whether to replace Quote</param>
 28     /// <param name="replaceImg">A value indicating whether to replace Img</param>
 29     /// <returns>Formatted text</returns>
 30     public static string FormatText(string text, bool replaceBold, bool replaceItalic,
 31         bool replaceUnderline, bool replaceUrl, bool replaceCode, bool replaceQuote, bool replaceImg)
 32     {
 33         if (String.IsNullOrEmpty(text))
 34             return string.Empty;
 35 
 36         if (replaceBold)
 37         {
 38             // format the bold tags: [b][/b]
 39             // becomes: <strong></strong>
 40             text = regexBold.Replace(text, "<strong>$1</strong>");
 41         }
 42 
 43         if (replaceItalic)
 44         {
 45             // format the italic tags: [i][/i]
 46             // becomes: <em></em>
 47             text = regexItalic.Replace(text, "<em>$1</em>");
 48         }
 49 
 50         if (replaceUnderline)
 51         {
 52             // format the underline tags: [u][/u]
 53             // becomes: <u></u>
 54             text = regexUnderLine.Replace(text, "<u>$1</u>");
 55         }
 56 
 57         if (replaceUrl)
 58         {
 59             var newWindow = EngineContext.Current.Resolve<CommonSettings>().BbcodeEditorOpenLinksInNewWindow;
 60             // format the url tags: [url=http://www.nopCommerce.com]my site[/url]
 61             // becomes: <a href="http://www.nopCommerce.com">my site</a>
 62             text = regexUrl1.Replace(text, string.Format("<a href="$1" rel="nofollow"{0}>$2</a>", newWindow ? " target=_blank" : ""));
 63 
 64             // format the url tags: [url]http://www.nopCommerce.com[/url]
 65             // becomes: <a href="http://www.nopCommerce.com">http://www.nopCommerce.com</a>
 66             text = regexUrl2.Replace(text, string.Format("<a href="$1" rel="nofollow"{0}>$1</a>", newWindow ? " target=_blank" : ""));
 67         }
 68 
 69         if (replaceQuote)
 70         {
 71             while (regexQuote.IsMatch(text))
 72                 text = regexQuote.Replace(text, "<b>$1 wrote:</b><div class="quote">$2</div>");
 73         }
 74 
 75         if (replaceCode)
 76         {
 77             text = CodeFormatHelper.FormatTextSimple(text);
 78         }
 79 
 80         if (replaceImg)
 81         {
 82             // format the img tags: [img]http://www.nopCommerce.com/Content/Images/Image.jpg[/img]
 83             // becomes: <img src="http://www.nopCommerce.com/Content/Images/Image.jpg">
 84             text = regexImg.Replace(text, "<img src="$1" class="user-posted-image" alt="">");
 85         }
 86         return text;
 87     }
 88 
 89     /// <summary>
 90     /// Removes all quotes from string
 91     /// </summary>
 92     /// <param name="str">Source string</param>
 93     /// <returns>string</returns>
 94     public static string RemoveQuotes(string str)
 95     {
 96         str = Regex.Replace(str, @"[quote=(.+?)]", String.Empty, RegexOptions.Compiled | RegexOptions.IgnoreCase);
 97         str = Regex.Replace(str, @"[/quote]", String.Empty, RegexOptions.Compiled | RegexOptions.IgnoreCase);
 98         return str;
 99     }
100 
101     #endregion
102 }

类型转换

public static int StrToInt(object obj, int? defaultVal)
{
    try
    {
        return Convert.ToInt32(obj);
    }
    catch
    {
        return defaultVal ?? 0;
    }
}

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原文地址：https://www.cnblogs.com/mantishell/p/10705199.html