C# FlowDocument 到 HTML 的转换

基本上，我有一个 RichTextBox，我想将其格式化内容转换为 HTML，以便它可以作为电子邮件发送。

我当前使用的方法根本不提供任何格式：

string message = new TextRange(messageTextBox.Document.ContentStart,
                               messageTextBox.Document.ContentEnd).Text;

所以我四处寻找并发现this然而，它已经存在超过 5 年了，并且在评论中一位 MSFT 用户评论说它不再受支持 -"This sample has been removed from our sample set and is no longer supported"，并且它生成的 HTML 格式比现代 HTML 或 XHTML 更旧，最好使用现代 HTML 或 XHTML。

谁能告诉我如何转换格式化的RichTextBox 的内容转换为 HTML？

（因此，当电子邮件发送时，收件人会看到带格式的电子邮件）

一般技术是使用XamlWriter来转换FlowDocument内容转换为 XML 流，然后使用 XSLT 转换将 XML 转换为 HTML。这并不是一个很好的答案，但那是因为任何给定的 FlowDocument 都有大量可能的 HTML 表示形式。

例如，此转换将每个顶级转换为Section to a div, every Paragraph to a p，以及每一个Run to a span谁的类告诉您它是斜体、粗体、下划线还是以上的任意组合。它对于我编写它的目的很有用，但称其为有损转换还算轻描淡写：

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet
    version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:msxsl="urn:schemas-microsoft-com:xslt"
    exclude-result-prefixes="msxsl x">

  <xsl:output method="xml" indent="yes" omit-xml-declaration="yes"/>

  <xsl:template match="x:Section[not(parent::x:Section)]">
    <div>
      <xsl:apply-templates select="node()"/>
    </div>
  </xsl:template>

  <xsl:template match="x:Section">
    <xsl:apply-templates select="node()"/>
  </xsl:template>

  <xsl:template match="x:Paragraph">
    <p>
      <xsl:apply-templates select="node()"/>
    </p>
  </xsl:template>

  <xsl:template match="x:Run">
    <xsl:variable name="class">
      <xsl:if test="@FontStyle='Italic'">
        <xsl:text>i </xsl:text>
      </xsl:if>
      <xsl:if test="@FontWeight='Bold'">
        <xsl:text>b </xsl:text>
      </xsl:if>
      <xsl:if test="contains(@TextDecorations, 'Underline')">
        <xsl:text>u </xsl:text>
      </xsl:if>
    </xsl:variable>
    <span>
      <xsl:if test="normalize-space($class) != ''">
        <xsl:attribute name="class">
          <xsl:value-of select="normalize-space($class)"/>
        </xsl:attribute>
      </xsl:if>
      <xsl:value-of select="text()"/>
    </span>
  </xsl:template>

</xsl:stylesheet>

这是我编写的用于进行转换的值转换器 - 请注意，为了使用值转换器，您还必须破解并实现一个版本RichTextBox将内容公开为依赖属性。确实，整个项目很痛苦。

public class FlowDocumentToHtmlConverter : IValueConverter
{
    private static XslCompiledTransform ToHtmlTransform;
    private static XslCompiledTransform ToXamlTransform;

    public FlowDocumentToHtmlConverter()
    {
        if (ToHtmlTransform == null)
        {
            ToHtmlTransform = LoadTransformResource("Converters/FlowDocumentToXhtml.xslt");
        }
        if (ToXamlTransform == null)
        {
            ToXamlTransform = LoadTransformResource("Converters/XhtmlToFlowDocument.xslt");
        }
    }
    private static XslCompiledTransform LoadTransformResource(string path)
    {
        Uri uri = new Uri(path, UriKind.Relative);
        XmlReader xr = XmlReader.Create(Application.GetResourceStream(uri).Stream);
        XslCompiledTransform xslt = new XslCompiledTransform();
        xslt.Load(xr);
        return xslt;
    }

    #region IValueConverter Members

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (!(value is FlowDocument))
        {
            return null;
        }
        if (targetType == typeof(FlowDocument))
        {
            return value;
        }

        if (targetType != typeof(string))
        {
            throw new InvalidOperationException(
                "FlowDocumentToHtmlConverter can only convert back from a FlowDocument to a string.");
        }

        FlowDocument d = (FlowDocument)value;

        using (MemoryStream ms = new MemoryStream())
        {
            // write XAML out to a MemoryStream
            TextRange tr = new TextRange(
                d.ContentStart,
                d.ContentEnd);
            tr.Save(ms, DataFormats.Xaml);
            ms.Seek(0, SeekOrigin.Begin);

            // transform the contents of the MemoryStream to HTML
            StringBuilder sb = new StringBuilder();
            using (StringWriter sw = new StringWriter(sb))
            {
                XmlWriterSettings xws = new XmlWriterSettings();
                xws.OmitXmlDeclaration = true;
                XmlReader xr = XmlReader.Create(ms);
                XmlWriter xw = XmlWriter.Create(sw, xws);
                ToHtmlTransform.Transform(xr, xw);
            }
            return sb.ToString();
        }
    }

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value == null)
        {
            return new FlowDocument();
        }
        if (value is FlowDocument)
        {
            return value;
        }
        if (targetType != typeof(FlowDocument))
        {
            throw new InvalidOperationException(
                "FlowDocumentToHtmlConverter can only convert to a FlowDocument.");
        }
        if (!(value is string))
        {
            throw new InvalidOperationException(
                "FlowDocumentToHtmlConverter can only convert from a string or FlowDocument.");
        }

        string s = (string)value;

        FlowDocument d;

        using (MemoryStream ms = new MemoryStream())
        using (StringReader sr = new StringReader(s))
        {
            XmlWriterSettings xws = new XmlWriterSettings();
            xws.OmitXmlDeclaration = true;
            using (XmlReader xr = XmlReader.Create(sr))
            using (XmlWriter xw = XmlWriter.Create(ms, xws))
            {
                ToXamlTransform.Transform(xr, xw);
            }
            ms.Seek(0, SeekOrigin.Begin);

            d = XamlReader.Load(ms) as FlowDocument;
        }
        XamlWriter.Save(d, Console.Out);
        return d;
    }

    #endregion
}