c# - Null reference on creating table with foreign key in Umbraco on application start -

i using umbraco 7.2.1 , wanted create table on application start. there 2 tables project , students, classes follows.

[tablename("projects")] public class project {     [primarykeycolumn(autoincrement=true)]     public int id { get; set; }      [required]     public string name { get; set; } } 

and

[tablename("students")] public class student {     [primarykeycolumn(autoincrement=true)]     public int id { get; set; }      [required]     public string name { get; set; }      [foreignkey(typeof(project))]     public int projectid { get; set; } } 

on application start checking if these table exists , if not creating them below

protected override void applicationstarted(umbracoapplicationbase umbracoapplication, applicationcontext applicationcontext) {     var db = applicationcontext.databasecontext.database;      //check if db table not exist     if (!db.tableexist("projects"))     {         //create db table - , set overwrite false         db.createtable<project>(false);     }     if (!db.tableexist("students"))     {         //here problem         //if student table not contain foreign key, works fine         db.createtable<student>(false);     }     base.applicationstarted(umbracoapplication, applicationcontext); } 

now, first table created without error, when reaches second table(students) there null reference error, know due foreign key have used, not know how solve this. stack trace below

[nullreferenceexception: object reference not set instance of object.]    umbraco.core.persistence.databasemodeldefinitions.definitionfactory.getforeignkeydefinition(type modeltype, propertyinfo propertyinfo, foreignkeyattribute attribute, string columnname, string tablename) +203    umbraco.core.persistence.databasemodeldefinitions.definitionfactory.gettabledefinition(type modeltype) +754    umbraco.core.persistence.petapocoextensions.createtable(database db, boolean overwrite, type modeltype) +100    umbraco.core.persistence.petapocoextensions.createtable(database db, boolean overwrite) +121    chatumbraco.app_code.umbracostartup.applicationstarted(umbracoapplicationbase umbracoapplication, applicationcontext applicationcontext) in d:\ecm\projects\umbraco\chatumbraco\chatumbraco\app_code\umbracostartup.cs:44    umbraco.core.applicationeventhandler.onapplicationstarted(umbracoapplicationbase umbracoapplication, applicationcontext applicationcontext) +62    umbraco.core.corebootmanager.<complete>b__5(iapplicationeventhandler x) +79    umbraco.core.enumerableextensions.foreach(ienumerable`1 items, action`1 action) +204    umbraco.core.corebootmanager.complete(action`1 aftercomplete) +185    umbraco.web.webbootmanager.complete(action`1 aftercomplete) +74    umbraco.core.umbracoapplicationbase.startapplication(object sender, eventargs e) +241    umbraco.core.umbracoapplicationbase.application_start(object sender, eventargs e) +40  [httpexception (0x80004005): object reference not set instance of object.]    system.web.httpapplicationfactory.ensureappstartcalledforintegratedmode(httpcontext context, httpapplication app) +9905705    system.web.httpapplication.registereventsubscriptionswithiis(intptr appcontext, httpcontext context, methodinfo[] handlers) +118    system.web.httpapplication.initspecial(httpapplicationstate state, methodinfo[] handlers, intptr appcontext, httpcontext context) +172    system.web.httpapplicationfactory.getspecialapplicationinstance(intptr appcontext, httpcontext context) +336    system.web.hosting.pipelineruntime.initializeapplication(intptr appcontext) +296  [httpexception (0x80004005): object reference not set instance of object.]    system.web.httpruntime.firstrequestinit(httpcontext context) +9885060    system.web.httpruntime.ensurefirstrequestinit(httpcontext context) +101    system.web.httpruntime.processrequestnotificationprivate(iis7workerrequest wr, httpcontext context) +254 

i added attribute primary key classes below , went well.

[tablename("projects")] [primarykey("id", autoincrement = true)] // missing public class project {     [primarykeycolumn(autoincrement=true)]     public int id { get; set; }      [required]     public string name { get; set; } }   [tablename("students")] [primarykey("id", autoincrement = true)] // missing //, affected class foreign key public class student {     [primarykeycolumn(autoincrement=true)]     public int id { get; set; }      [required]     public string name { get; set; }      [foreignkey(typeof(project))]     public int projectid { get; set; } }