entity framework - N to M relationship code first does not create the foreign key on the M-table -

a schoolclasscode can have many pupils.

a pupil can belong many schoolclasscodes.

this n m relation.

i thought n m relation work in code first default.

but explicitly create n m relation here:

    modelbuilder.entity<schoolclasscode>().                   hasmany(c => c.pupils).                   withmany(p => p.schoolclasscodes).                   map(                    m =>                    {                        m.mapleftkey("schoolclasscodeid");                        m.maprightkey("pupilid");                        m.totable("schoolclasscodepupil");                    });  public class schoolclasscode     {         public schoolclasscode()         {             pupils = new hashset<pupil>();             tests = new hashset<test>();         }          public int id { get; set; }         public string schoolclasscodename { get; set; }         public string subjectname { get; set; }         public int color { get; set; }         public string classidentifier { get; set; }         public iset<pupil> pupils { get; set; }         public iset<test> tests { get; set; }         public schoolyear schoolyear { get; set; }         public int schoolyearid { get; set; }     }  public class pupil     {         public pupil()         {             pupilstests = new hashset<pupiltest>();             schoolclasscodes = new hashset<schoolclasscode>();         }          public int id { get; set; }         public string firstname { get; set; }         public string lastname { get; set; }         public string postal { get; set; }         public string city { get; set; }         public string street { get; set; }         public iset<pupiltest> pupilstests { get; set; }         public iset<schoolclasscode> schoolclasscodes { get; set; }     } 

on pupil table no foreign key created @ all, why this?

for many many relationship, there no foreign key on either side. foreign keys on join table, have mapped table schoolclasscodepupil:

modelbuilder.entity<schoolclasscode>().              hasmany(c => c.pupils).              withmany(p => p.schoolclasscodes).              map(m =>                  {                      m.mapleftkey("schoolclasscodeid");                      m.maprightkey("pupilid");                      m.totable("schoolclasscodepupil");                  }); 

entity framework uses junction table determine belongs in somepupil.schoolclasscodes set.