using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.IO;

namespace ConsoleApplication1
{
    class Program
    {
        public static string XmlGet(string link, string name)
        {
            XmlTextReader reader = new XmlTextReader(link);
            while (reader.Read())
            {
                if (reader.NodeType == XmlNodeType.Element && name.Equals(reader.LocalName))
                {
                    return reader.ReadElementContentAsString();
                }
            }
            return string.Empty;
        }
        static void Main(string[] args)
        {
            string xml = @"http://api.vkontakte.ru/api.php?api_id=652647&method=getGroups&sig=48af6f2fb49c3727745d800d964df178";
            string b = XmlGet(xml, "error");
Console.WriteLine(b);
Console.ReadLine();

        }
    }
}