c# - Intermittent error Linq to NHibernate Sequence Contains no Elements -

this may sound duplicate question, don't believe is.

this error i'm getting, sounds common. i'm getting error intermittently. number of users site, i'm estimating occurs 5% of time.

here's code:

private topwrestlers filltopwrestlers() {     try     {         var mostrecent = _wrestlerrankingrepo.query().orderbydescending(wr => wr.season).first().season;         var currentseason = _configservice.getcurrentseason();          if (mostrecent > currentseason)             return null;          var tws =             _wrestlerrankingrepo.getrankedwrestlers(currentseason)                 .where(wr => wr.rank <= 3)                 .orderby(wr => wr.rank)                 .select(wr => wr.wrestler);          return new topwrestlers         {             _125 = tws.firstordefault(w => w.roster.weightclass == 125),             _133 = tws.firstordefault(w => w.roster.weightclass == 133),             _141 = tws.firstordefault(w => w.roster.weightclass == 141),             _149 = tws.firstordefault(w => w.roster.weightclass == 149),             _157 = tws.firstordefault(w => w.roster.weightclass == 157),             _165 = tws.firstordefault(w => w.roster.weightclass == 165),             _174 = tws.firstordefault(w => w.roster.weightclass == 174),             _184 = tws.firstordefault(w => w.roster.weightclass == 184),             _197 = tws.firstordefault(w => w.roster.weightclass == 197),             _285 = tws.firstordefault(w => w.roster.weightclass == 285)         };     }     catch (exception ex)     {         _errorservice.logerror(new exception("exception occurred trying retrieve top wrestlers each weight on home page. " + ex.message, ex));         return null;     } } 

i'm getting error on first line:

_wrestlerrankingrepo.query().orderbydescending(wr => wr.season).first().season; 

i know repo has data. since returns fine 95% of time.

any on how can figure out how fix bug? i'm not able re-create issue. on homepage of site. don't believe has new session firing up....i'm @ loss here.

here's base repo code:

public abstract class baserepository<trecord, tmap> : ibaserepository<trecord>     trecord : class, ientity     tmap : classmap<trecord>, new() {     private static member _primarykeymember;     protected isession session;     protected iuseridentity useridentity;      public baserepository(isession session)     {         session = session;     }      public baserepository(isession session, iuseridentity useridentity)     {         session = session;         useridentity = useridentity;     }      public void delete(trecord obj)     {         session.delete(obj);         session.flush();     }      public void save(trecord value)     {         session.saveorupdate(value);         session.flush();     }      public void save(ienumerable<trecord> values)     {         using (itransaction sessiontransaction = session.begintransaction())         {             try             {                 foreach (trecord value in values)                     session.saveorupdate(value);                  sessiontransaction.commit();                 session.flush();             }             catch             {                 sessiontransaction.rollback();                 throw;             }         }     }      public virtual iqueryable<trecord> query()     {         return session.query<trecord>();     } }  public interface ibaserepository<trecord>     trecord : ientity {     void delete(trecord obj);      void save(trecord value);     void save(ienumerable<trecord> values);     iqueryable<trecord> query(); } 

and here's wrestlerrankingrepo code:

public class wrestlerrankingrepository : baserepository<wrestlerranking, wrestlerrankingmap>, iwrestlerrankingrepository {     public wrestlerrankingrepository(isession session) : base(session)     {     }      public iqueryable<wrestlerranking> getrankedwrestlers(int season)     {         return base.query()             .where(wr => wr.rank != null)             .where(wr => wr.season == season)             .where(wr => wr.iscurrent)             .where(wr => !wr.wrestler.lastname.startswith("("));     }      public iqueryable<wrestlerranking> getrankedwrestlers(int season, int weight)     {         return getrankedwrestlers(season)             .where(wr => wr.weightclass == weight);     }      public iqueryable<wrestlerranking> getrankedwrestlerswithmatches(int season)     {         return getrankedwrestlers(season);         // reason hates this: .where(w => w.currentstats != null)     }      public iqueryable<wrestlerranking> getrankedwrestlerswithmatches(int season, int weight)     {         return getrankedwrestlers(season)             .where(w => w.weightclass == weight);         // reason hates this: .where(w => w.currentstats != null)     } }  public interface iwrestlerrankingrepository : ibaserepository<wrestlerranking> {     iqueryable<wrestlerranking> getrankedwrestlers(int season);     iqueryable<wrestlerranking> getrankedwrestlers(int season, int weight);     iqueryable<wrestlerranking> getrankedwrestlerswithmatches(int season);     iqueryable<wrestlerranking> getrankedwrestlerswithmatches(int season, int weight); } 

sessionfactory code:

public static class sessionfactory {     private static isessionprovider _instance;      public static isessionprovider instance     {                 {             if (_instance == null)             {                 string sessionclass = configurationmanager.appsettings["sessionprovider"];                  if (string.isnullorwhitespace(sessionclass))                     throw new configurationerrorsexception("session provider must specified in app.config");                  _instance = (isessionprovider)activator.createinstance(type.gettype(sessionclass));             }              return _instance;         }     }      [obsolete]     public static isession getcurrentsession()     {         return getsession();     }      public static isession getsession()     {         return instance.getsession();     }      public static string getconnectionstring()     {         return configurationmanager.connectionstrings["wrestlestat"].connectionstring;     }      public static ipersistenceconfigurer buildconfig()     {         return mssqlconfiguration.mssql2008.connectionstring(getconnectionstring());     }      public static void buildmappings(mappingconfiguration mappings)     {         mappings.fluentmappings.addfromassembly(assembly.getexecutingassembly());     } }  public class sqlstatementinterceptor : emptyinterceptor {     public override sqlstring onpreparestatement(sqlstring sql)     {         trace.writeline(sql.tostring());         return sql;     } }  public interface isessionprovider {     isession getsession();     isession opensession();     void closesession(); } 

here's ninject impelementation:

private static void registerservices(ikernel kernel)     {         kernel.bind(scanner => scanner                                    .from(new list<assembly>                                              {                                                  typeof (homecontroller).assembly,                                                  typeof (match).assembly                                              })                                    .selectallclasses()                                    .bindallinterfaces()                                    .configure(b => b.intransientscope())             );          kernel.rebind<isession>().tomethod(icontext => sessionfactory.getsession()).inrequestscope();         //kernel.rebind<iuseridentity>().tomethod(i => mvcapplication.getwebidentity()).inrequestscope();     } 

another spot that's relevant...

public class corewebsessionmodule : ihttpmodule {     public void init(httpapplication context)     {         context.beginrequest += opensession;         context.endrequest += closesession;     }      private static void opensession(object sender, eventargs e)     {         sessionfactory.instance.opensession();     }      private static void closesession(object sender, eventargs e)     {         sessionfactory.instance.closesession();     }      public void dispose()     {     } } 

one more

public class corewebsessionprovider : isessionprovider     {         private static isessionfactory _holder;          private static isessionfactory mysessionfactory         {                         {                 if (_holder == null)                 {                     _holder = getfluentconfiguration().buildsessionfactory();                 }                  return _holder;             }         }          public isession getsession()         {             return httpcontext.current != null ? mysessionfactory.getcurrentsession() : null;         }          public isession opensession()         {             var session = mysessionfactory.opensession();             managedwebsessioncontext.bind(httpcontext.current, session);             return session;         }          public void closesession()         {             var session = managedwebsessioncontext.unbind(httpcontext.current, mysessionfactory);              if (session != null)             {                 if (session.transaction != null && session.transaction.isactive)                     session.transaction.rollback();                 //else                 //    session.flush();                  if (session.isopen)                     session.close();             }         }          private static fluentconfiguration getfluentconfiguration()         {             return                 fluently.configure()                         .database(sessionfactory.buildconfig())                         .exposeconfiguration(buildschema)                         .mappings(sessionfactory.buildmappings);         }          public static configuration getconfiguration()         {             return getfluentconfiguration().buildconfiguration();         }          private static void buildschema(configuration config)         {             config.setproperty("current_session_context_class", "managed_web");         }          public istatelesssession getstatelesssession()         {             return mysessionfactory.openstatelesssession();         }     } 

from nhibernate documentation (emphasis mine):

an isessionfactory expensive-to-create, threadsafe object intended shared application threads. isession inexpensive, non-threadsafe object should used once, single business process, , discarded

so should not sharing session object around this. if possible, create 1 when needed , destroy possible.

some excellent further reading here talks context , lifetime, including nhibernate.