C# Online Compiler | .NET Fiddle

using System;
using Newtonsoft.Json;
using System.Xml;
using System.Xml.Linq;
using System.Net;
using System.IO;


public class Program
{
	public static void Main()
	{


            WebClient web = new WebClient();
            var value = web.DownloadString("http://powdertoy.co.uk/Browse/Comments.json?ID=1681176&Start=0&Count=20");

            string json = @"{
   '?xml': {
     '@version': '1.0',
     '@standalone': 'no'
   },
   'root': {
     'minhaclasse':
[
" + value.Replace("'", "\'") + @"

]
  }
}";

            XmlDocument xml = (XmlDocument)JsonConvert.DeserializeXmlNode(json);


            var xmlString = xml.InnerXml;


            using (XmlReader reader = XmlReader.Create(new StringReader(xmlString)))
            {
                reader.MoveToContent();
                while (reader.Read())
                {
                    if (reader.NodeType == XmlNodeType.Element)
                    {

                        
                        if (reader.Name == "Username")
                        {
                            XElement el = XNode.ReadFrom(reader) as XElement;
                            if (el != null)
                            {
                                Console.Write("Username : ");
                                Console.WriteLine(el.Value);
                            }
                        }
                    }
                }
            }	}
}

 
using System;
using Newtonsoft.Json;
using System.Xml;
using System.Xml.Linq;
using System.Net;
using System.IO;
​
​
public class Program
{
    public static void Main()
    {
​
​
            WebClient web = new WebClient();
            var value = web.DownloadString("http://powdertoy.co.uk/Browse/Comments.json?ID=1681176&Start=0&Count=20");
​
            string json = @"{
   '?xml': {
     '@version': '1.0',
     '@standalone': 'no'
   },
   'root': {
     'minhaclasse':