No session bound to the current context

Friends, I have the following problem, when compiling my application it returns me the 

following error: No session bound to the current context. I use NhibernateHelper, and 

the error appears in this line of code:

public static ISession GetSessao()  
       {  
           return Instance.GetSessionFactory().GetCurrentSession();  
       }  
Como posso resolver esse erro?

Segue meu código completo:

using System;  
using System.Collections.Generic;  
using System.Linq;  
using System.Text;  
using NHibernate.Mapping.Attributes;  
using NHibernate.Cfg;  
using NHibernate;  
using System.IO;  
using NHibernate.Context;  
  
namespace SDPJDominio.DataAccess  
{  
    public class NhibernateHelper  
    {  
        private ISessionFactory sessionFactory;          
          
        public static ISession GetSessao()  
        {  
            return Instance.GetSessionFactory().GetCurrentSession();  
        }  
  
        public static ISessionFactory Teste()  
        {  
            MemoryStream stream = new System.IO.MemoryStream();  
            HbmSerializer.Default.Validate = true;  
            HbmSerializer.Default.Serialize(stream, System.Reflection.Assembly.GetExecutingAssembly());  
            stream.Position = 0;  
            Configuration configuration= new Configuration();              
            configuration.Configure();  
            configuration.SetProperty("connection.connection_string", ConfigNhibernate.getConfig());   
            configuration.SetProperty("current_session_context_class", "thread_static");   
            configuration.AddInputStream(stream);  
            stream.Close();  
  
            Instance.sessionFactory = configuration.BuildSessionFactory();  
            return Instance.sessionFactory;  
        }  
         
        public NhibernateHelper()  
        {                      
            MemoryStream stream = new System.IO.MemoryStream();  
            HbmSerializer.Default.Validate = true;  
            HbmSerializer.Default.Serialize(stream, System.Reflection.Assembly.GetExecutingAssembly());  
            stream.Position = 0;  
            Configuration configuration= new Configuration();  
            configuration.Configure();  
            configuration.SetProperty("connection.connection_string", ConfigNhibernate.getConfig());                   
            configuration.AddInputStream(stream);  
            stream.Close();  
                  
            sessionFactory = configuration.BuildSessionFactory();              
        }  
  
        public static ISessionFactory SessionFactory  
        {  
            get { return Instance.sessionFactory; }  
        }  
  
        private ISessionFactory GetSessionFactory()  
        {  
            return sessionFactory;  
        }  
  
        public static NhibernateHelper Instancia  
        {  
            get   
            {  
                returnCreateSessionKey.gerenciadorDeSessao;   
            }  
        }  
  
        public static ISession OpeningSession()  
        {  
            return Instance.GetSessionFactory().OpenSession();  
        }  
  
        public static void ReloadSession(object obj)  
        {  
            CurrentSession.Refresh(obj);  
        }  
  
        public static ISession ReloadSession  
        {  
            get  
            {  
                return Instance.GetSessionFactory().GetCurrentSession();  
            }  
        }  
  
        class CreateSessionKey  
        {  
            internal static readonly NhibernateHelper SESSIONMANAGER= new NhibernateHelper();  
        }     
    }  
}  
Could you kindly help me?