c# - Nhibernate null referrence exception during database connection -

i getting exception when program starting connection ms sql 2005 express db on windows xp. got error , not... nhibernate v3

dbmonitor class runs on separate thread, on one, future can run on multiple.

i have similar sessionprovidermssql2005 class sqlite connection , has same issue , session provider sqlite runs on multiple threads...

system.nullreferenceexception: object reference not set instance of object.    @ system.collections.generic.dictionary`2.insert(tkey key, tvalue value, boolean add)    @ system.collections.generic.dictionary`2.set_item(tkey key, tvalue value)    @ nhibernate.impl.sessionfactoryobjectfactory.addinstance(string uid, string name,         isessionfactory instance, idictionary`2 properties)    @ nhibernate.impl.sessionfactoryimpl..ctor(configuration cfg, imapping mapping, settings settings, eventlisteners listeners)    @ nhibernate.cfg.configuration.buildsessionfactory()    @ mysolution.databaselayer.repositories.sessionprovidermssql2005.get_sessionfactory()    @ mysolution.databaselayer.repositories.sessionprovidermssql2005.opensession() 

there sessionprovidermssql2005 class

using system; using system.collections.generic; using nhibernate; using nhibernate.cfg; using environment = nhibernate.cfg.environment;  namespace mysolution.databaselayer.repositories {     public class sessionprovidermssql2005     {         private static readonly object _padlock = new object();          private static configuration _configuration;         public static configuration configuration         {                         {                 lock (_padlock)//must thread save!                 {                     if (_configuration == null)                     {                          if (string.isnullorempty(initialcatalog))                         {                             throw new nullreferenceexception("property initialcatalog not null or empty!");                         }                          if (string.isnullorempty(servername))                         {                             throw new nullreferenceexception("property servername not null or empty!");                         }                          _configuration = new configuration();                         _configuration.configure("config/hibernate.mssql2005.cfg.xml");                         _configuration.addassembly("mysolution.databaselayer");                         configuration.addproperties(new dictionary<string, string>                                                       {                                                          { environment.connectionstring, @"server="+servername+";initial catalog="+initialcatalog+";integrated security=sspi;" }                                                      });                     }                     return _configuration;                 }             }         }          private static isessionfactory _sessionfactory;         public static isessionfactory sessionfactory         {                     {             lock (_padlock)             {                 if (_sessionfactory == null)                 {                     lock (_padlock)                     {                         _sessionfactory = configuration.buildsessionfactory();                     }                 }                 return _sessionfactory;             }         }         }          public static string servername { get; set; }         public static string initialcatalog { get; set; }           private sessionprovidermssql2005()         { }          public static isession opensession()         {             lock (_padlock)             {                 return sessionfactory.opensession();             }         }          public static void closesession()         {             lock (_padlock)             {                 sessionfactory.close();             }         }     } } 

i using class this:

 public class dbmonitor {     private isession _session;       public dbmonitor(string servername, string initialcatalog)     {         sessionprovidermssql2005.servername = servername;         sessionprovidermssql2005.initialcatalog = initialcatalog;     }      public void start()     {       _session = sessionprovidermssql2005.opensession();       ilist data = _session.createsqlquery("select * sometable id = 1").list();        ...      }    } 

any idea cause this?

update: correction of sessionfactory getter. correct?

this multi-threading issue, not directly related nhibernate, see same question , answer here: throw nullreferenceexception while calling set_item method of dictionary object in multi-threding scenario