你如何将Html转换为纯文本？

Question

我有一个存储在表格中的Html片段.不是整页,没有标签等,只是基本的格式.

我希望能够在给定页面上显示Html仅作为文本,没有格式化(实际上只是前30到50个字符,但这很容易).

如何将该Html中的"文本"作为直文放入字符串中？

所以这段代码.

<b>Hello World.</b><br/><p><i>Is there anyone out there?</i><p>

变为:

你好,世界.有没有人在那里？

Answer 1

的自由和开源HtmlAgilityPack具有在其样品中的一个,从HTML转换为纯文本的方法.

var plainText = HtmlUtilities.ConvertToPlainText(string html);

给它一个HTML字符串

<b>你好世界!</ b> <br /> <i>是我!!</ I>

你会得到一个纯文本结果,如:

<b>hello, <i>world!</i></b>

Answer 2

我无法使用HtmlAgilityPack,所以我为自己写了第二个最佳解决方案

private static string HtmlToPlainText(string html)
{
    const string tagWhiteSpace = @"(>|$)(\W|\n|\r)+<";//matches one or more (white space or line breaks) between '>' and '<'
    const string stripFormatting = @"<[^>]*(>|$)";//match any character between '<' and '>', even when end tag is missing
    const string lineBreak = @"<(br|BR)\s{0,1}\/{0,1}>";//matches: <br>,<br/>,<br />,<BR>,<BR/>,<BR />
    var lineBreakRegex = new Regex(lineBreak, RegexOptions.Multiline);
    var stripFormattingRegex = new Regex(stripFormatting, RegexOptions.Multiline);
    var tagWhiteSpaceRegex = new Regex(tagWhiteSpace, RegexOptions.Multiline);

    var text = html;
    //Decode html specific characters
    text = System.Net.WebUtility.HtmlDecode(text); 
    //Remove tag whitespace/line breaks
    text = tagWhiteSpaceRegex.Replace(text, "><");
    //Replace <br /> with line breaks
    text = lineBreakRegex.Replace(text, Environment.NewLine);
    //Strip formatting
    text = stripFormattingRegex.Replace(text, string.Empty);

    return text;
}

Answer 3

如果您正在谈论标签剥离,那么如果您不必担心<script>标签这样的问题,则相对简单.如果您只需显示没有标记的文本,则可以使用正则表达式完成该操作:

<[^>]*>

如果你不必担心<script>标签等,那么你需要比正则表达式更强大的功能,因为你需要跟踪状态,更像是一个Context Free Grammar(CFG).虽然你可以通过"从左到右"或非贪婪的匹配来完成它.

如果您可以使用正则表达式,那么有很多网页都有很好的信息:

• http://weblogs.asp.net/rosherove/archive/2003/05/13/6963.aspx
• http://www.google.com/search?hl=en&q=html+tag+stripping+&btnG=Search

如果您需要更复杂的CFG行为,我建议使用第三方工具,不幸的是我不知道推荐的好方法.

Answer 4

HTTPUtility.HTMLEncode()用于将HTML标记编码为字符串.它会为您解决所有繁重的工作.从MSDN文档:

如果在HTTP流中传递诸如空白和标点符号之类的字符,则它们可能在接收端被误解释.HTML编码将HTML中不允许的字符转换为字符实体等价物; HTML解码反转了编码.例如,当嵌入在文本块中时,字符<和>被编码为<和>HTTP传输.

HTTPUtility.HTMLEncode()方法,详述在这里:

public static void HtmlEncode(
  string s,
  TextWriter output
)

用法:

String TestString = "This is a <Test String>.";
StringWriter writer = new StringWriter();
Server.HtmlEncode(TestString, writer);
String EncodedString = writer.ToString();

Answer 5

要添加到vfilby的答案,您只需在代码中执行RegEx替换; 不需要新的课程.如果像我这样的其他新手在这个问题上遇到困难.

using System.Text.RegularExpressions;

然后...

private string StripHtml(string source)
{
        string output;

        //get rid of HTML tags
        output = Regex.Replace(source, "<[^>]*>", string.Empty);

        //get rid of multiple blank lines
        output = Regex.Replace(output, @"^\s*$\n", string.Empty, RegexOptions.Multiline);

        return output;
}

Answer 6

更新2023年的答案。答案与往常基本相同：

1. 安装最新的HtmlAgilityPack

2. 创建一个名为HtmlUtilities 的实用程序类，它使用 HtmlAgilityPack。

3. 用它：var plainText = HtmlUtilities.ConvertToPlainText(email.HtmlCode);

以下是从上面的链接复制的 HtmlUtilities 类：

using HtmlAgilityPack;
using System;
using System.IO;

namespace ReadSharp
{
public class HtmlUtilities
{
/// <summary>
/// Converts HTML to plain text / strips tags.
/// </summary>
/// <param name="html">The HTML.</param>
/// <returns></returns>
public static string ConvertToPlainText(string html)
{
  HtmlDocument doc = new HtmlDocument();
  doc.LoadHtml(html);

  StringWriter sw = new StringWriter();
  ConvertTo(doc.DocumentNode, sw);
  sw.Flush();
  return sw.ToString();
}


/// <summary>
/// Count the words.
/// The content has to be converted to plain text before (using ConvertToPlainText).
/// </summary>
/// <param name="plainText">The plain text.</param>
/// <returns></returns>
public static int CountWords(string plainText)
{
  return !String.IsNullOrEmpty(plainText) ? plainText.Split(' ', '\n').Length : 0;
}


public static string Cut(string text, int length)
{
  if (!String.IsNullOrEmpty(text) && text.Length > length)
  {
    text = text.Substring(0, length - 4) + " ...";
  }
  return text;
}


private static void ConvertContentTo(HtmlNode node, TextWriter outText)
{
  foreach (HtmlNode subnode in node.ChildNodes)
  {
    ConvertTo(subnode, outText);
  }
}


private static void ConvertTo(HtmlNode node, TextWriter outText)
{
  string html;
  switch (node.NodeType)
  {
    case HtmlNodeType.Comment:
      // don't output comments
      break;

    case HtmlNodeType.Document:
      ConvertContentTo(node, outText);
      break;

    case HtmlNodeType.Text:
      // script and style must not be output
      string parentName = node.ParentNode.Name;
      if ((parentName == "script") || (parentName == "style"))
        break;

      // get text
      html = ((HtmlTextNode)node).Text;

      // is it in fact a special closing node output as text?
      if (HtmlNode.IsOverlappedClosingElement(html))
        break;

      // check the text is meaningful and not a bunch of whitespaces
      if (html.Trim().Length > 0)
      {
        outText.Write(HtmlEntity.DeEntitize(html));
      }
      break;

    case HtmlNodeType.Element:
      switch (node.Name)
      {
        case "p":
          // treat paragraphs as crlf
          outText.Write("\r\n");
          break;
        case "br":
          outText.Write("\r\n");
          break;
      }

      if (node.HasChildNodes)
      {
        ConvertContentTo(node, outText);
      }
      break;
  }
}
}
}

Answer 7

将HTML转换为纯文本的三步过程

首先你需要为HtmlAgilityPack安装Nuget包 第二次创建这个类

public class HtmlToText
{
    public HtmlToText()
    {
    }

    public string Convert(string path)
    {
        HtmlDocument doc = new HtmlDocument();
        doc.Load(path);

        StringWriter sw = new StringWriter();
        ConvertTo(doc.DocumentNode, sw);
        sw.Flush();
        return sw.ToString();
    }

    public string ConvertHtml(string html)
    {
        HtmlDocument doc = new HtmlDocument();
        doc.LoadHtml(html);

        StringWriter sw = new StringWriter();
        ConvertTo(doc.DocumentNode, sw);
        sw.Flush();
        return sw.ToString();
    }

    private void ConvertContentTo(HtmlNode node, TextWriter outText)
    {
        foreach(HtmlNode subnode in node.ChildNodes)
        {
            ConvertTo(subnode, outText);
        }
    }

    public void ConvertTo(HtmlNode node, TextWriter outText)
    {
        string html;
        switch(node.NodeType)
        {
            case HtmlNodeType.Comment:
                // don't output comments
                break;

            case HtmlNodeType.Document:
                ConvertContentTo(node, outText);
                break;

            case HtmlNodeType.Text:
                // script and style must not be output
                string parentName = node.ParentNode.Name;
                if ((parentName == "script") || (parentName == "style"))
                    break;

                // get text
                html = ((HtmlTextNode)node).Text;

                // is it in fact a special closing node output as text?
                if (HtmlNode.IsOverlappedClosingElement(html))
                    break;

                // check the text is meaningful and not a bunch of whitespaces
                if (html.Trim().Length > 0)
                {
                    outText.Write(HtmlEntity.DeEntitize(html));
                }
                break;

            case HtmlNodeType.Element:
                switch(node.Name)
                {
                    case "p":
                        // treat paragraphs as crlf
                        outText.Write("\r\n");
                        break;
                }

                if (node.HasChildNodes)
                {
                    ConvertContentTo(node, outText);
                }
                break;
        }
    }
}

通过使用上面的课程参考Judah Himango的答案

第三,你需要创建上面的类的对象和使用ConvertHtml(HTMLContent)方法将HTML转换为纯文本而不是ConvertToPlainText(string html);

HtmlToText htt=new HtmlToText();
var plainText = htt.ConvertHtml(HTMLContent);

Answer 8

它的局限性在于它不会折叠长的行内空格，但绝对是可移植的，并且尊重Web浏览器之类的布局。

static string HtmlToPlainText(string html) {
  string buf;
  string block = "address|article|aside|blockquote|canvas|dd|div|dl|dt|" +
    "fieldset|figcaption|figure|footer|form|h\\d|header|hr|li|main|nav|" +
    "noscript|ol|output|p|pre|section|table|tfoot|ul|video";

  string patNestedBlock = $"(\\s*?</?({block})[^>]*?>)+\\s*";
  buf = Regex.Replace(html, patNestedBlock, "\n", RegexOptions.IgnoreCase);

  // Replace br tag to newline.
  buf = Regex.Replace(buf, @"<(br)[^>]*>", "\n", RegexOptions.IgnoreCase);

  // (Optional) remove styles and scripts.
  buf = Regex.Replace(buf, @"<(script|style)[^>]*?>.*?</\1>", "", RegexOptions.Singleline);

  // Remove all tags.
  buf = Regex.Replace(buf, @"<[^>]*(>|$)", "", RegexOptions.Multiline);

  // Replace HTML entities.
  buf = WebUtility.HtmlDecode(buf);
  return buf;
}

Answer 9

我认为最简单的方法是创建一个“字符串”扩展方法（基于用户理查德的建议）：

using System;
using System.Text.RegularExpressions;

public static class StringHelpers
{
    public static string StripHTML(this string HTMLText)
        {
            var reg = new Regex("<[^>]+>", RegexOptions.IgnoreCase);
            return reg.Replace(HTMLText, "");
        }
}

然后只需在程序中的任何“字符串”变量上使用此扩展方法即可：

var yourHtmlString = "<div class=\"someclass\"><h2>yourHtmlText</h2></span>";
var yourTextString = yourHtmlString.StripHTML();

我使用这个扩展方法将 html 格式的注释转换为纯文本，以便它可以正确显示在水晶报表上，并且效果完美！