Untitled

string html ='<html>
   <body>
      <p left-margin="0" style="margin:0 0 11 0;text-align:Left;">Hi</p>
      <p left-margin="0" style="margin:0 0 11 0;text-align:Left;font-style:italic;">
         <span style="font-style:normal;" />
      </p>
      <p left-margin="0" style="margin:0 0 11 0;text-align:Left;">
         <span style="font-style:italic;" />
         Kodi
      </p>
   </body>
</html>'

string html = Utilities.GetHtmlContent(richText).RemoveInvalidXmlCharacters();
    Html = html;

if (!string.IsNullOrEmpty(text))
{
    var xmlPattern = "[^x09x0Ax0Dx20-xD7FFxE000-xFFFDx10000-x10FFFF]";
    return Regex.Replace(text, xmlPattern, string.Empty);
}

string html ='<html>
   <body>
      <p left-margin="0" style="margin:0 0 11 0;text-align:Left;">Hi</p>
      <p left-margin="0" style="margin:0 0 11 0;text-align:Left;font-style:italic;">
      </p>
      <p left-margin="0" style="margin:0 0 11 0;text-align:Left;">
         <span style="font-style:italic;" />
         Kodi
      </p>
   </body>
</html>'