c# - The type not mapped issue -

i have class in domain-project :

public class person: entityobject {     public int id { get; set; }     public string name { get; set; } } 

i have repository in dataaccess-project:

public class personrepository {     databasecontext dbcontext { get; }      public personrepository(databasecontext dbcontext)     {         this.dbcontext = dbcontext;     }      public virtual ienumerable<person> getall()     {         return dbcontext.persons.tolist();     }      public virtual void savechanges(person persoon)     {          // configure auditing         dbcontext.audit<person, personhistory>(             (record, action) => new personhistory()             {                 id = record.field<person, int>(f => f.id),                 name = record.field<person, string>(f => f.name),                 createddate = datetime.now,                 createdby = "simon",                 changedby = "simon",                 changeddate = datetime.now,                 changetype = action.tostring()             },             (ph) => dbcontext.personhistory.add(ph));          dbcontext.savechanges();     } } 

my dbcontext in dataaccess-project , looks follows:

public class databasecontext : dbcontext {     public databasecontext()     {         database.setinitializer<databasecontext>(null);     }      protected override void onmodelcreating(dbmodelbuilder modelbuilder)     {         modelbuilder.conventions.remove<pluralizingtablenameconvention>();     }      public virtual dbset<person> persons { get; set; }      public virtual dbset<personhistory> personhistory { get; set; } } 

i've added extension-method provide audittrailing.

public static class dbcontextextension {     public static void audit<tfromtype, ttotype>(this dbcontext context,func<idatarecord, entitystate, ttotype> mapping,action<ttotype> addtocontext)     {         objectcontext ctx = ((iobjectcontextadapter)context).objectcontext;         ctx.savingchanges += new eventhandler((o, e) => createauditrecord<tfromtype, ttotype>(ctx, mapping, addtocontext));     }      private static void createauditrecord<tfromtype, ttotype>(        objectcontext context,        func<idatarecord, entitystate, ttotype> mapping,        action<ttotype> addtocontext)     {         // list of changes audit         ienumerable<objectstateentry> entities =             e in context.objectstatemanager.getobjectstateentries(                 entitystate.modified | entitystate.deleted)                             e.isrelationship == false &&                 typeof(tfromtype).isassignablefrom(e.entity.gettype())             select e;          foreach (objectstateentry item in entities)         {             // map changed item audit record entry             ttotype auditrecord = mapping(item.originalvalues, item.state);             // , add object context persisted             addtocontext(auditrecord);         }     }      public static t field<e, t>(this idatarecord record, expression<func<e, t>> propertyselector)         e : entityobject     {         memberexpression memberexpression = propertyselector.body memberexpression;         memberinfo propertyinfo = memberexpression.member;          int fieldindex = record.getordinal(propertyinfo.name);         return field<t>(record, fieldindex);     }      public static t field<t>(this idatarecord record, int ordinal)     {         object value = record.isdbnull(ordinal) ? null : record.getvalue(ordinal);         return (t)value;     } } 

now when run application following error:

an exception of type 'system.invalidoperationexception' occurred in entityframework.dll not handled in user code

additional information: type 'coben.dossier.domain.person' not mapped. check type has not been explicitly excluded using ignore method or notmappedattribute data annotation. verify type defined class, not primitive or generic, , not inherit entityobject.

what doing wrong ?