Converting RTF to HTML

MattManela — Mon, 28 Sep 2009 21:28:00 GMT

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

The two most important WPF Tools

MattManela — Fri, 01 Aug 2008 18:49:00 GMT

I have been working a lot with WPF and I found the following two FREE tools to be extremely helpful.

The first is:

XamlPadX - (http://blogs.msdn.com/llobo/archive/2007/12/19/xamlpadx-v3-0.aspx)

This is an enhanced version of XamlPad which comes with the .NET SDK. This is a light weight tool which parses and renders XAML code visually. It adds (in addition to just rendering XAML) a command interpreter, visual tree explorer, add-in support and much more.

I find this tool very usefull when I want to just play around with XAML and see how things render. It is quicker than firing up VS and using the Cider designer.

The other tool is:

Snoop - (http://www.blois.us/Snoop/)

Snoop is a visual debugger for WPF application. When any WPF application is running you can use snoop to view its visual tree and all the elements properties. You can search for any element, view its properties, change its properties and see how the application changes.

This program really helps in understanding what is going on in your WPF application and finding problems.

Matt Manela's Blog : XAML

Converting RTF to HTML

The two most important WPF Tools