如何在C#中剥离RTF标签提取内嵌的HTML内容？

我有一段内嵌HTML格式的RTF字符串（如下所示），需要用C#代码剥离RTF标签，提取出完整的HTML内容。之前尝试过提取纯文本的方案，但没能得到理想结果，求可行的实现方法。

{\rtf1\ansi\ansicpg1252\fromhtml1 \fbidis \deff0{\fonttbl
{\f0\fswiss Arial;}
{\f1\fmodern Courier New;}
{\f2\fnil\fcharset2 Symbol;}
{\f3\fmodern\fcharset0 Courier New;}}
{\colortbl\red0\green0\blue0;\red0\green0\blue255;}
\uc1\pard\plain\deftab360 \f0\fs24 
{\*\htmltag19 <html>}
{\*\htmltag34 <head>}
{\*\htmltag1 \par }
{\*\htmltag1 \par }
{\*\htmltag41 </head>}
{\*\htmltag2 \par }
{\*\htmltag50 <body>}
{\*\htmltag0 \par }
{\*\htmltag96 <div>}\htmlrtf {\htmlrtf0 
{\*\htmltag112 <br>}\htmlrtf \par
\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag112 <br>}\htmlrtf \par
\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag112 <br>}\htmlrtf \par
\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="width:100%;height:20px;">}\htmlrtf {\htmlrtf0 {\*\htmltag64}\htmlrtf {\htmlrtf0 
{\*\htmltag148 <span style="white-space:nowrap;color:#5F5F5F;opacity:.36;">}\htmlrtf {\htmlrtf0 ________________________________________________________________________________
{\*\htmltag156 </span>}\htmlrtf }\htmlrtf0 
{\*\htmltag4 \par }\htmlrtf  \htmlrtf0 {\*\htmltag72}\htmlrtf\par}\htmlrtf0

{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div class="me-email-text" lang="en-US" style="color:#252424;font-family:'Segoe UI','Helvetica Neue',Helvetica,Arial,sans-serif;">}\htmlrtf {\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="margin-top:24px;margin-bottom:20px;">}\htmlrtf {\htmlrtf0 {\*\htmltag64}\htmlrtf {\htmlrtf0 
{\*\htmltag148 <span style="font-size:24px;color:#252424;">}\htmlrtf {\htmlrtf0 Microsoft Teams meeting
{\*\htmltag156 </span>}\htmlrtf }\htmlrtf0 
{\*\htmltag4 \par }\htmlrtf  \htmlrtf0 {\*\htmltag72}\htmlrtf\par}\htmlrtf0

{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="margin-bottom:20px;">}\htmlrtf {\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="margin-top:0px;margin-bottom:0px;font-weight:bold;">}\htmlrtf {\htmlrtf0 {\*\htmltag64}\htmlrtf {\htmlrtf0 
{\*\htmltag148 <span style="font-size:14px;color:#252424;">}\htmlrtf {\htmlrtf0 Join on your computer or mobile app
{\*\htmltag156 </span>}\htmlrtf }\htmlrtf0 
{\*\htmltag4 \par }\htmlrtf  \htmlrtf0 {\*\htmltag72}\htmlrtf\par}\htmlrtf0

{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }{\*\htmltag64}\htmlrtf {\htmlrtf0 {}
{\*\htmltag84 <a href="https://teams.microsoft.com/l/meetup-join/19%3ameeting_NmEzYjM0YTAtMzljNC00YWUyLTk0NWQtYmQxYTAxNWRhOWFi%40thread.v2/0?context=%7b%22Tid%22%3a%2204930c22-8e5a-4c3c-88d9-5d040b723d74%22%2c%22Oid%22%3a%2265834454-14e9-4f1e-9b41-3a214f3f285c%22%7d" class="me-email-headline" style="font-size:14px;font-family:'Segoe UI Semibold','Segoe UI','Helvetica Neue',Helvetica,Arial,sans-serif;text-decoration:underline;color:#6264a7;" title="https://teams.microsoft.com/l/meetup-join/19%3ameeting_nmezyjm0ytatmzljnc00ywuyltk0nwqtymqxytaxnwrhowfi%40thread.v2/0?context=%7b%22tid%22%3a%2204930c22-8e5a-4c3c-88d9-5d040b723d74%22%2c%22oid%22%3a%2265834454-14e9-4f1e-9b41-3a214f3f285c%22%7d" target="_blank" rel="noreferrer noopener">}\htmlrtf {\field{\*\fldinst{HYPERLINK "https://teams.microsoft.com/l/meetup-join/19%3ameeting_NmEzYjM0YTAtMzljNC00YWUyLTk0NWQtYmQxYTAxNWRhOWFi%40thread.v2/0?context=%7b%22Tid%22%3a%2204930c22-8e5a-4c3c-88d9-5d040b723d74%22%2c%22Oid%22%3a%2265834454-14e9-4f1e-9b41-3a214f3f285c%22%7d" \n}}{\fldrslt\cf1\ul \htmlrtf0 Click
{\*\htmltag4 \par }\htmlrtf  \htmlrtf0 
{\*\htmltag4  }here to join the meeting\htmlrtf }\htmlrtf0 \htmlrtf }\htmlrtf0 
{\*\htmltag92 </a>} {\*\htmltag72}\htmlrtf\par}\htmlrtf0

{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="margin-bottom:24px;margin-top:20px;">}\htmlrtf {\htmlrtf0 {\*\htmltag64}\htmlrtf {\htmlrtf0 {}
{\*\htmltag84 <a href="https://aka.ms/JoinTeamsMeeting" class="me-email-link" style="font-size:14px;text-decoration:underline;color:#6264a7;font-family:'Segoe UI','Helvetica Neue',Helvetica,Arial,sans-serif;" title="https://aka.ms/jointeamsmeeting" target="_blank" rel="noreferrer noopener">}\htmlrtf {\field{\*\fldinst{HYPERLINK "https://aka.ms/JoinTeamsMeeting" \n}}{\fldrslt\cf1\ul \htmlrtf0 Learn
{\*\htmltag4 \par }\htmlrtf  \htmlrtf0 
{\*\htmltag4  }More\htmlrtf }\htmlrtf0 \htmlrtf }\htmlrtf0 
{\*\htmltag92 </a>} | {}
{\*\htmltag84 <a href="https://teams.microsoft.com/meetingOptions/?organizerId=65834454-14e9-4f1e-9b41-3a214f3f285c&tenantId=04930c22-8e5a-4c3c-88d9-5d040b723d74&threadId=19_meeting_NmEzYjM0YTAtMzljNC00YWUyLTk0NWQtYmQxYTAxNWRhOWFi@thread.v2&messageId=0&language=en-US" class="me-email-link" style="font-size:14px;text-decoration:underline;color:#6264a7;font-family:'Segoe UI','Helvetica Neue',Helvetica,Arial,sans-serif;" title="https://teams.microsoft.com/meetingoptions/?organizerid=65834454-14e9-4f1e-9b41-3a214f3f285c&tenantid=04930c22-8e5a-4c3c-88d9-5d040b723d74&threadid=19_meeting_nmezyjm0ytatmzljnc00ywuyltk0nwqtymqxytaxnwrhowfi@thread.v2&messageid=0&language=en-us" target="_blank" rel="noreferrer noopener">}\htmlrtf {\field{\*\fldinst{HYPERLINK "https://teams.microsoft.com/meetingOptions/?organizerId=65834454-14e9-4f1e-9b41-3a214f3f285c&tenantId=04930c22-8e5a-4c3c-88d9-5d040b723d74&threadId=19_meeting_NmEzYjM0YTAtMzljNC00YWUyLTk0NWQtYmQxYTAxNWRhOWFi@thread.v2&messageId=0&language=en-US" \n}}{\fldrslt\cf1\ul \htmlrtf0 
{\*\htmltag4 \par }Meeting options\htmlrtf }\htmlrtf0 \htmlrtf }\htmlrtf0 
{\*\htmltag92 </a>} {\*\htmltag72}\htmlrtf\par}\htmlrtf0

{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="font-size:14px;margin-bottom:4px;font-family:'Segoe UI','Helvetica Neue',Helvetica,Arial,sans-serif;">}\htmlrtf {\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="font-size:12px;">}\htmlrtf {\htmlrtf0 
{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div style="width:100%;height:20px;">}\htmlrtf {\htmlrtf0 {\*\htmltag64}\htmlrtf {\htmlrtf0 
{\*\htmltag148 <span style="white-space:nowrap;color:#5F5F5F;opacity:.36;">}\htmlrtf {\htmlrtf0 ________________________________________________________________________________
{\*\htmltag156 </span>}\htmlrtf }\htmlrtf0 
{\*\htmltag4 \par }\htmlrtf  \htmlrtf0 {\*\htmltag72}\htmlrtf\par}\htmlrtf0

{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag96 <div>}\htmlrtf {\htmlrtf0 
{\*\htmltag104 </div>}\htmlrtf }\htmlrtf0 
{\*\htmltag0 \par }
{\*\htmltag58 </body>}
{\*\htmltag2 \par }
{\*\htmltag27 </html>}
{\*\htmltag3 \par }}

解决方案 #

针对这种内嵌HTML的RTF，有三种可靠的实现方式：

方法1：正则表达式提取（轻量无依赖） #

观察RTF结构可知，所有HTML标签都包裹在{\*\htmltag\d+ (.*?)}格式块中，文本内容则出现在\htmlrtf0之后、下一个RTF标签之前。通过正则匹配提取这些内容，再拼接成完整HTML：

using System;
using System.Text.RegularExpressions;

public class RtfHtmlExtractor
{
    public static string ExtractHtmlFromRtf(string rtfContent)
    {
        // 提取所有htmltag中的HTML标签
        var htmlTagMatches = Regex.Matches(rtfContent, @"\{\*\\htmltag\d+ (.*?)\}", RegexOptions.Singleline);
        // 提取所有htmlrtf0后的文本内容
        var textMatches = Regex.Matches(rtfContent, @"\htmlrtf0\s*(.*?)(?=\\htmlrtf|\{\*\\htmltag|\z)", RegexOptions.Singleline);

        var htmlBuilder = new System.Text.StringBuilder();
        int textIndex = 0;

        foreach (Match tagMatch in htmlTagMatches)
        {
            string tagContent = tagMatch.Groups[1].Value;
            // 替换RTF转义字符
            tagContent = tagContent.Replace(""", "\"")
                                   .Replace("&lt;", "<")
                                   .Replace("&gt;", ">");
            
            htmlBuilder.Append(tagContent);

            // 追加对应文本内容
            if (textIndex < textMatches.Count)
            {
                string textContent = textMatches[textIndex].Groups[1].Value.Trim();
                // 去除RTF格式标记
                textContent = Regex.Replace(textContent, @"\\par\s*", "\n");
                if (!string.IsNullOrWhiteSpace(textContent))
                {
                    htmlBuilder.Append(textContent);
                }
                textIndex++;
            }
        }

        // 清理多余换行和空格
        string finalHtml = Regex.Replace(htmlBuilder.ToString(), @"\n\s*\n", "\n");
        return finalHtml.Trim();
    }
}

方法2：使用WinForms RichTextBox控件（适配复杂RTF） #

利用.NET自带的RichTextBox加载RTF后导出为HTML，能处理包含复杂格式的RTF内容：

using System.Windows.Forms;
using System.IO;

public class RtfHtmlConverter
{
    public static string ConvertRtfToHtml(string rtfContent)
    {
        using (var richTextBox = new RichTextBox())
        {
            richTextBox.Rtf = rtfContent;
            using (var htmlStream = new MemoryStream())
            {
                richTextBox.SaveFile(htmlStream, RichTextBoxStreamType.Html);
                htmlStream.Seek(0, SeekOrigin.Begin);
                using (var reader = new StreamReader(htmlStream))
                {
                    return reader.ReadToEnd();
                }
            }
        }
    }
}

注意：该方法需引用System.Windows.Forms程序集，控制台或ASP