Converting RTF to HTML
Have you ever had the desire to convert some RTF text into HTML? Probably not. But if you do, then you are in luck! I recently had the need to do this conversion and after some searching found out a way to do it by enhancing a sample distributed in the MSDN library. The sample is called: XAML to HTML Conversion Demo.
The sample has code which converts HTML to and from a XAML Flow Document. But this doesn’t make things easier until you realize that there is a way to convert RTF to XAML easily. The key is to use System.Windows.Controls.RichTextBox which can load RTF from a stream and save it as XAML. This conversion is shown below:
private static string ConvertRtfToXaml(string rtfText)
{
var richTextBox = new RichTextBox();
if (string.IsNullOrEmpty(rtfText)) return "";
var textRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
using (var rtfMemoryStream = new MemoryStream())
{
using (var rtfStreamWriter = new StreamWriter(rtfMemoryStream))
{
rtfStreamWriter.Write(rtfText);
rtfStreamWriter.Flush();
rtfMemoryStream.Seek(0, SeekOrigin.Begin);
textRange.Load(rtfMemoryStream, DataFormats.Rtf);
}
}
using (var rtfMemoryStream = new MemoryStream())
{
textRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
textRange.Save(rtfMemoryStream, DataFormats.Xaml);
rtfMemoryStream.Seek(0, SeekOrigin.Begin);
using (var rtfStreamReader = new StreamReader(rtfMemoryStream))
{
return rtfStreamReader.ReadToEnd();
}
}
}
With this code we have all we need to convert RTF to HTML. I modified the sample to add this RTF To XAML conversation and then I run that XAML through HTML converter which results in the HTML text. I added an interface to these conversion utilities and converted the sample into a library so that I would be able to use it from other projects. Here is the interface:
public interface IMarkupConverter
{
string ConvertXamlToHtml(string xamlText);
string ConvertHtmlToXaml(string htmlText);
string ConvertRtfToHtml(string rtfText);
}
public class MarkupConverter : IMarkupConverter
{
public string ConvertXamlToHtml(string xamlText)
{
return HtmlFromXamlConverter.ConvertXamlToHtml(xamlText, false);
}
public string ConvertHtmlToXaml(string htmlText)
{
return HtmlToXamlConverter.ConvertHtmlToXaml(htmlText, true);
}
public string ConvertRtfToHtml(string rtfText)
{
return RtfToHtmlConverter.ConvertRtfToHtml(rtfText);
}
}
With this I am now able to convert from RTF to HTML. However, there is one catch - the conversion uses the RichTextBox WPF control which requires a single threaded apartment (STA). Therefore in order to run your code that calls the ConvertRtfToHtml function, it must also be running in a STA. If you can’t have your program run in a STA then you must create a new STA thread to run the conversion. Like this:
MarkupConverter markupConverter = new MarkupConverter();
private string ConvertRtfToHtml(string rtfText)
{
var thread = new Thread(ConvertRtfInSTAThread);
var threadData = new ConvertRtfThreadData { RtfText = rtfText };
thread.SetApartmentState(ApartmentState.STA);
thread.Start(threadData);
thread.Join();
return threadData.HtmlText;
}
private void ConvertRtfInSTAThread(object rtf)
{
var threadData = rtf as ConvertRtfThreadData;
threadData.HtmlText = markupConverter.ConvertRtfToHtml(threadData.RtfText);
}
private class ConvertRtfThreadData
{
public string RtfText { get; set; }
public string HtmlText { get; set; }
}
Here is the zip contain the code for the Markup converter: MarkupConverter.zip
Comments
Anonymous
June 06, 2010
Hi First thanks and u have done a good job, I am using the dll to convert rtf to html in ssrs 2008 project (rdl files) My problem is that rdl dosn't support the style text-decoration:underline. What changes need to be done in the dll to use the tag U ThanksAnonymous
August 10, 2010
Can it be vice versa? I mean can I covert from HTML to RTF? Thank you very much