Any third Party tool (dll) to convert Content of WPF Rich Text box to HTML?

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; }