How to get list of object and their relation details from database without entity frameworkk

Hi all,
I want to get primary key table details as list of object and their relation in same object with list of other object without using entity framework.

i am able to convert primary key table details in list of object after converting datatable to list using generic method but how can i get list of foreign key table details in same object. i don't want to use entiry framework .please help .thanks in advance.
my class details below
public class Orderdetails
int orderid;
int id;
int qty;


public class userdetails
public int id { get; set; }
public string name { get; set; }
public string address { get; set; }
public string phone { get; set; }
public string pin { get; set; }
public int type { get; set; }
public List<Orderdetails> order { get; set; }

i want to get like list<userdetails> and inside that list<Orderdetails>