c# - Default Id generating 00000 in MongoDb -

i have db structure follow .

public class university     {         [bsonid]         public objectid id { get; set; }         public string name { get; set; }         public string code { get; set; }         public ilist<college> colleges { get; set; }     }     public class college     {         [bsonid]         public objectid id { get; set; }         public string name { get; set; }         public string code { get; set; }     } 

as can see, university can have multiple colleges . i'm adding data follow

ilist<college> lstcolleges=new list<college>();      college clg1=new college(){         name="clg1",         code="clg1001"     };      college clg2=new college(){         name="clg2",         code="clg1002"     };      lstcolleges.add(clg1);     lstcolleges.add(clg2);      university unv=new university(){         name="univ",         code="un101",         colleges=lstcolleges     };     var collections = mongodatabase.getcollection<university>("university");         collections.insert(unv);         var id = student.unv; 

it correctly generating id university, every college, it's generating 000000.

i want generate different default id each colleges.

only top level _id automatically assigned.
in embedded document need manually generated.

you in ctor:

public class college {     public  college      {         id = objectid.generatenewid();             }      [bsonid]     public objectid id { get; set; }     public string name { get; set; }     public string code { get; set; } }