System.IO.StringWriter.ToString C# (CSharp) Méthode

        public override string ToString()
        {
            return _sb.ToString();
        }
    }

 public static string GetWellFormedHTML(string html, string xpathNavPath)
 {
     // StreamReader sReader = null;
     StringWriter sw = null;
     SgmlReader reader = null;
     XmlTextWriter writer = null;
     try
     {
         //  if (uri == String.Empty) uri = "http://www.XMLforASP.NET";
         // HttpWebRequest req = (HttpWebRequest)WebRequest.Create(uri);
         //  HttpWebResponse res = (HttpWebResponse)req.GetResponse();
         //  sReader = new StreamReader(res.GetResponseStream());
         reader = new SgmlReader();
         reader.DocType = "HTML";
         reader.InputStream = new StringReader(html);
         sw = new StringWriter();
         writer = new XmlTextWriter(sw);
         writer.Formatting = Formatting.Indented;
         //writer.WriteStartElement("Test");
         while (reader.Read())
         {
             if (reader.NodeType != XmlNodeType.Whitespace)
             {
                 writer.WriteNode(reader, true);
             }
         }
         //writer.WriteEndElement();
         if (xpathNavPath == null)
         {
             string sr = sw.ToString();
             sr = sr.Replace("\r", "\n");
             sr = sr.Replace("\n\n", "\n");
             return sr;
         }
         else
         { //Filter out nodes from HTML
             StringBuilder sb = new StringBuilder();
             XPathDocument doc = new XPathDocument(new StringReader(sw.ToString()));
             XPathNavigator nav = doc.CreateNavigator();
             XPathNodeIterator nodes = nav.Select(xpathNavPath);
             while (nodes.MoveNext())
             {
                 sb.Append(nodes.Current.Value + "\n");
             }
             string sr = sb.ToString();
             sr = sr.Replace("\r", "\n");
             sr = sr.Replace("\n\n", "\n");
             return sr;
         }
     }
     catch (Exception exp)
     {
         writer.Close();
         reader.Close();
         sw.Close();
         // sReader.Close();
         return exp.Message;
     }
 }