public Boolean AddUser(CUser user)
 {
     return(Invoke(new CDbOperationInvoker <Boolean>((context) =>
     {
         context.Users.Add(user);
         context.Authentications.Add(user.Authentication);
         context.SaveChanges();
         return true;
     })));
 }
 public CUser FindRegisteredUser(String nickname)
 {
     return(Invoke(new CDbOperationInvoker <CUser>((context) =>
     {
         CUser entry = context.Users.FirstOrDefault(user => user.Nickname == nickname);
         if (entry == null)
         {
             return null;
         }
         context.Entry(entry).Reference("Authentication").Load();
         return entry;
     })));
 }