如何在C#中将HTML转换为文本？

Question

我正在寻找C#代码将HTML文档转换为纯文本.

我不是在寻找简单的标签剥离,而是要输出纯文本,并合理保留原始布局.

输出应如下所示:

W3C的Html2Txt

我看过HTML Agility Pack,但我认为这不是我需要的.有没有人有任何其他建议？

编辑:我只是从CodePlex下载HTML Agility Pack ,并运行Html2Txt项目.多么令人失望(至少是html到文本转换的模块)!所有这一切都是剥离标签,压平表等.输出看起来不像Html2Txt @ W3C产生的.太糟糕了,这个来源似乎不可用.我当时想看看是否有更多的"罐装"解决方案.

编辑2:谢谢大家的建议. FlySwat向我倾斜了我想去的方向.我可以使用System.Diagnostics.Process类的"突降"开关运行lynx.exe将文本发送到标准输出,并与捕获标准输出ProcessStartInfo.UseShellExecute = false和ProcessStartInfo.RedirectStandardOutput = true.我将把所有这些包装在一个C#类中.这个代码只会偶尔被调用,所以我不太关心产生一个新进程而不是代码执行它.另外,Lynx很快!

Answer 1

关于后人的HtmlAgilityPack的一个注释.该项目包含一个将文本解析为html的示例,正如OP所指出的那样,它根本不像处理HTML所设想的任何人那样处理空格.有全文渲染解决方案在那里,别人这个问题,这,这不是(它甚至不能处理目前的形式表)所指出的,但它重量轻,速度快,这是我想要创建一个简单的文本HTML电子邮件的版本.

using System.IO;
using System.Text.RegularExpressions;
using HtmlAgilityPack;

//small but important modification to class https://github.com/zzzprojects/html-agility-pack/blob/master/src/Samples/Html2Txt/HtmlConvert.cs
public static class HtmlToText
{

    public static string Convert(string path)
    {
        HtmlDocument doc = new HtmlDocument();
        doc.Load(path);
        return ConvertDoc(doc);
    }

    public static string ConvertHtml(string html)
    {
        HtmlDocument doc = new HtmlDocument();
        doc.LoadHtml(html);
        return ConvertDoc(doc);
    }

    public static string ConvertDoc (HtmlDocument doc)
    {
        using (StringWriter sw = new StringWriter())
        {
            ConvertTo(doc.DocumentNode, sw);
            sw.Flush();
            return sw.ToString();
        }
    }

    internal static void ConvertContentTo(HtmlNode node, TextWriter outText, PreceedingDomTextInfo textInfo)
    {
        foreach (HtmlNode subnode in node.ChildNodes)
        {
            ConvertTo(subnode, outText, textInfo);
        }
    }
    public static void ConvertTo(HtmlNode node, TextWriter outText)
    {
        ConvertTo(node, outText, new PreceedingDomTextInfo(false));
    }
    internal static void ConvertTo(HtmlNode node, TextWriter outText, PreceedingDomTextInfo textInfo)
    {
        string html;
        switch (node.NodeType)
        {
            case HtmlNodeType.Comment:
                // don't output comments
                break;
            case HtmlNodeType.Document:
                ConvertContentTo(node, outText, textInfo);
                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.Length == 0)
                {
                    break;
                }
                if (!textInfo.WritePrecedingWhiteSpace || textInfo.LastCharWasSpace)
                {
                    html= html.TrimStart();
                    if (html.Length == 0) { break; }
                    textInfo.IsFirstTextOfDocWritten.Value = textInfo.WritePrecedingWhiteSpace = true;
                }
                outText.Write(HtmlEntity.DeEntitize(Regex.Replace(html.TrimEnd(), @"\s{2,}", " ")));
                if (textInfo.LastCharWasSpace = char.IsWhiteSpace(html[html.Length - 1]))
                {
                    outText.Write(' ');
                }
                    break;
            case HtmlNodeType.Element:
                string endElementString = null;
                bool isInline;
                bool skip = false;
                int listIndex = 0;
                switch (node.Name)
                {
                    case "nav":
                        skip = true;
                        isInline = false;
                        break;
                    case "body":
                    case "section":
                    case "article":
                    case "aside":
                    case "h1":
                    case "h2":
                    case "header":
                    case "footer":
                    case "address":
                    case "main":
                    case "div":
                    case "p": // stylistic - adjust as you tend to use
                        if (textInfo.IsFirstTextOfDocWritten)
                        {
                            outText.Write("\r\n");
                        }
                        endElementString = "\r\n";
                        isInline = false;
                        break;
                    case "br":
                        outText.Write("\r\n");
                        skip = true;
                        textInfo.WritePrecedingWhiteSpace = false;
                        isInline = true;
                        break;
                    case "a":
                        if (node.Attributes.Contains("href"))
                        {
                            string href = node.Attributes["href"].Value.Trim();
                            if (node.InnerText.IndexOf(href, StringComparison.InvariantCultureIgnoreCase)==-1)
                            {
                                endElementString =  "<" + href + ">";
                            }  
                        }
                        isInline = true;
                        break;
                    case "li": 
                        if(textInfo.ListIndex>0)
                        {
                            outText.Write("\r\n{0}.\t", textInfo.ListIndex++); 
                        }
                        else
                        {
                            outText.Write("\r\n*\t"); //using '*' as bullet char, with tab after, but whatever you want eg "\t->", if utf-8 0x2022
                        }
                        isInline = false;
                        break;
                    case "ol": 
                        listIndex = 1;
                        goto case "ul";
                    case "ul": //not handling nested lists any differently at this stage - that is getting close to rendering problems
                        endElementString = "\r\n";
                        isInline = false;
                        break;
                    case "img": //inline-block in reality
                        if (node.Attributes.Contains("alt"))
                        {
                            outText.Write('[' + node.Attributes["alt"].Value);
                            endElementString = "]";
                        }
                        if (node.Attributes.Contains("src"))
                        {
                            outText.Write('<' + node.Attributes["src"].Value + '>');
                        }
                        isInline = true;
                        break;
                    default:
                        isInline = true;
                        break;
                }
                if (!skip && node.HasChildNodes)
                {
                    ConvertContentTo(node, outText, isInline ? textInfo : new PreceedingDomTextInfo(textInfo.IsFirstTextOfDocWritten){ ListIndex = listIndex });
                }
                if (endElementString != null)
                {
                    outText.Write(endElementString);
                }
                break;
        }
    }
}
internal class PreceedingDomTextInfo
{
    public PreceedingDomTextInfo(BoolWrapper isFirstTextOfDocWritten)
    {
        IsFirstTextOfDocWritten = isFirstTextOfDocWritten;
    }
    public bool WritePrecedingWhiteSpace {get;set;}
    public bool LastCharWasSpace { get; set; }
    public readonly BoolWrapper IsFirstTextOfDocWritten;
    public int ListIndex { get; set; }
}
internal class BoolWrapper
{
    public BoolWrapper() { }
    public bool Value { get; set; }
    public static implicit operator bool(BoolWrapper boolWrapper)
    {
        return boolWrapper.Value;
    }
    public static implicit operator BoolWrapper(bool boolWrapper)
    {
        return new BoolWrapper{ Value = boolWrapper };
    }
}

例如,以下HTML代码......

<!DOCTYPE HTML>
<html>
    <head>
    </head>
    <body>
        <header>
            Whatever Inc.
        </header>
        <main>
            <p>
                Thanks for your enquiry. As this is the 1<sup>st</sup> time you have contacted us, we would like to clarify a few things:
            </p>
            <ol>
                <li>
                    Please confirm this is your email by replying.
                </li>
                <li>
                    Then perform this step.
                </li>
            </ol>
            <p>
                Please solve this <img alt="complex equation" src="http://upload.wikimedia.org/wikipedia/commons/8/8d/First_Equation_Ever.png"/>. Then, in any order, could you please:
            </p>
            <ul>
                <li>
                    a point.
                </li>
                <li>
                    another point, with a <a href="http://en.wikipedia.org/wiki/Hyperlink">hyperlink</a>.
                </li>
            </ul>
            <p>
                Sincerely,
            </p>
            <p>
                The whatever.com team
            </p>
        </main>
        <footer>
            Ph: 000 000 000<br/>
            mail: whatever st
        </footer>
    </body>
</html>

......将转变为:

Whatever Inc. 


Thanks for your enquiry. As this is the 1st time you have contacted us, we would like to clarify a few things: 

1.  Please confirm this is your email by replying. 
2.  Then perform this step. 

Please solve this [complex equation<http://upload.wikimedia.org/wikipedia/commons/8/8d/First_Equation_Ever.png>]. Then, in any order, could you please: 

*   a point. 
*   another point, with a hyperlink<http://en.wikipedia.org/wiki/Hyperlink>. 

Sincerely, 

The whatever.com team 


Ph: 000 000 000
mail: whatever st 

......而不是:

        Whatever Inc.


            Thanks for your enquiry. As this is the 1st time you have contacted us, we would like to clarify a few things:

                Please confirm this is your email by replying.

                Then perform this step.


            Please solve this . Then, in any order, could you please:

                a point.

                another point, with a hyperlink.


            Sincerely,


            The whatever.com team

        Ph: 000 000 000
        mail: whatever st

Answer 2

你可以用这个:

 public static string StripHTML(string HTMLText, bool decode = true)
        {
            Regex reg = new Regex("<[^>]+>", RegexOptions.IgnoreCase);
            var stripped = reg.Replace(HTMLText, "");
            return decode ? HttpUtility.HtmlDecode(stripped) : stripped;
        }

更新

感谢我更新的评论以改进此功能

Answer 3

我从一个可靠的消息来源获悉,如果你在.Net中进行HTML解析,你应该再次查看HTML敏捷包.

http://www.codeplex.com/htmlagilitypack

一些样本在SO ..

HTML Agility包 - 解析表

Answer 4

您正在寻找的是一个文本模式DOM渲染器,它可以输出文本,就像Lynx或其他文本浏览器......这比你想象的要难得多.