c# - How to make join between two entities, if entity framework doesn't map the junction entity? -

i have many many relationiship, i'm using ef, don't have junction table, because doesn't have primary key.

usually, if tableab had primary key, i'd make this:

var query = in db.tablea             join ab in db.tableab on             a.id equals ab.id_tablea             join b in db.tableb on             ab.id_tableb equals b.id             select { a.field, b.field }; 

but, don't have mapped tableab, correct way join?

i've created navigation properties, using api fluent mapping. using navigation properties data, performance it's worse, or not?

edit: i'm using poco.

thanks

as understood question, tableab has composite primary key [id_tablea, id_tableb]. think it's better make correct mapping of key. should that:

public class tableab {     [key]     [column(order = 0)]     [foreignkey("tablea")]     public int id_tablea { get; set; }      [key]     [column(order = 1)]     [foreignkey("tableb")]     public int id_tableb{ get; set; } 

}