My game freezes whenever i use a function which involves http?

 My game freezes whenever i use any fucntion which includes any http calls. I mean the game is waiting for the data to get completed eveything else stops in the mean time. Like the sprite animations,game time,etc..
 
 
 
 Example:
 
  
 
     public PendingGamesByUser GetPendingGamesByUser(string userName)
             {
                 XmlNode xmlNodes = null;
                 PendingGamesByUser pendingGamesByUser = new PendingGamesByUser();
                 List<PendingGamesYourTurn> pendingGamesYourTurns = new List<PendingGamesYourTurn>();
                 List<PendingGamesTheirTurn> pendingGamesTheirTurns = new List<PendingGamesTheirTurn>();
                 HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(string.Concat("http://www.poquere.com/gotchha/getPendingGames.php?name=", userName));
                 HttpWebResponse response = (HttpWebResponse)httpWebRequest.GetResponse();
                 string end = (new StreamReader(response.GetResponseStream())).ReadToEnd();
                 XmlDocument xmlDocument = new XmlDocument();
                 xmlDocument.LoadXml(end);
                 string empty = string.Empty;
                 foreach (XmlNode xmlNodes in xmlDocument.SelectNodes("//response/data/yourturn"))
                 {
                     empty = xmlNodes.InnerText;
                     PendingGamesYourTurn pendingGamesYourTurn = new PendingGamesYourTurn();
                     pendingGamesYourTurns.Add(JsonConvert.DeserializeObject<PendingGamesYourTurn>(empty));
                 }
                 foreach (XmlNode xmlNodes1 in xmlDocument.SelectNodes("//response/data/theirturn"))
                 {
                     empty = xmlNodes1.InnerText;
                     PendingGamesTheirTurn pendingGamesTheirTurn = new PendingGamesTheirTurn();
                     pendingGamesTheirTurns.Add(JsonConvert.DeserializeObject<PendingGamesTheirTurn>(empty));
                 }
                 pendingGamesByUser.PendingYourTurn = pendingGamesYourTurns.ToArray();
                 pendingGamesByUser.PendingTheirTurn = pendingGamesTheirTurns.ToArray();
                 return pendingGamesByUser;
             }

When i call the above function like below

pendinggame = GetPendingGamesByUser("kannan21jan");

it lags right there. How to solve this?