Insert and delete from "associations table on EF model" - linq

Question

I have to tables "ALUMNOS" and "MATERIAS". In SQL exist another table "ALUMNOS BY MATERIAS". I know this is not necessary in EF model, because exists the properties navigation. But how can insert or delete from this " associations table"??
Thanks in advance!!
Guille

Answer 1

The only way would be to remove the link between the Materia and Alumno objects before saving again. This way they are individual objects or only contain links that are required. This will set the mapping table correctly.

Answer 2

Created the tables and got the objects like you have got. To insert a new row, I do the following
StackExchangeExampleEntities exchangeExampleEntities = new StackExchangeExampleEntities();
Alumno alumno = new Alumno() {AlumId = 2, Description = "aldesc"};
Materia materia = new Materia() {materia_Id = 2, description = "mdesc"};
materia.Alumnos.Add(alumno);// attach the relationship
exchangeExampleEntities.Materias.Add(materia);
exchangeExampleEntities.SaveChanges();
To Delete the mapping table, I clear down the collection in one side ( you can use either collection - Alumno or materia)
StackExchangeExampleEntities exchangeExampleEntities = new StackExchangeExampleEntities();
Materia materiaFetched = exchangeExampleEntities.Materias.Single(m => m.materia_Id == 2);
materiaFetched.Alumnos.Clear();
exchangeExampleEntities.SaveChanges();
If you just want the mapping table to be used, then add a new entityframework file and then select only the mapping table( dont select any thing else). This will create entity just for this mapping table in the context.
Now you can use it like this:
StackExchangeExampleEntities1 exchangeExampleEntities1 = new StackExchangeExampleEntities1();
MateriaAlumono s = exchangeExampleEntities1.MateriaAlumonoes.First();
Console.WriteLine(s.Alumuno_id);