Code First EF 4.1 : Building Many to Many Relationship

Since we do not have any designer question might arise how can we create Many to Many relationship in Code First 4.1. Here it is

 public class Emp
{
    public Emp()
    {
        Projects = new HashSet<Project>();
    }

    public int EmpId { get; set; }
    public string EmpName { get; set; }
    public ICollection<Project> Projects { get; set; }
}

public class Project
{
    public Project()
    {
        Emps = new HashSet<Emp>();
    }

    public int ProjectId { get; set; }
    public string ProjectName { get; set; }
    public ICollection<Emp> Emps { get; set; }
}

public class EmpContext : DbContext
{
    public DbSet<Emp> Emps { get; set; }
    public DbSet<Project> Projects { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        var p1 = new Project() { ProjectName = "Fun Boat" };
        var p2 = new Project() { ProjectName = "Jumbo Jet" };
        var p3 = new Project() { ProjectName = "Free Zoo" };

        var e1 = new Emp() { EmpName = "Wriju" };
        var e2 = new Emp() { EmpName = "Wrishika" };
        var e3 = new Emp() { EmpName = "Saswati" };

        p1.Emps.Add(e1);
        p1.Emps.Add(e2);

        p2.Emps.Add(e2);
        p2.Emps.Add(e3);

        p3.Emps.Add(e3);
        p3.Emps.Add(e1);

        using (var ctx = new EmpContext())
        {
            ctx.Projects.Add(p1);
            ctx.Projects.Add(p2);
            ctx.Projects.Add(p3);
                
            ctx.SaveChanges();
        }
    }
}

Generated database would look like

Namoskar!!!

Comments

• Anonymous
  July 08, 2011
  Nice! Thanks. Now I'm wondering: What if I already have an existing list of Emp's? I want to associate the Project with some of those existing Emps. How would I do that? Your code above creates brand new Emps and adds those to the Emp table.

• Anonymous
  July 20, 2011
  Please tell me how to Add、Delete、Modify Data??

• Anonymous
  August 04, 2011
  if ProjectEmps has some properties: Weight ... how to add delete update   thanks a lot

• Anonymous
  February 06, 2012
  How can I add some data to the ProjectEmps table? i.e. LastActivity:date, Commission:money etc.

• Anonymous
  February 06, 2012
  To add to the child table you need to first get the employee to an object from DB then use it instead of creating new. After it should look the same.

• Anonymous
  April 12, 2012
  thank's but i have this database : commande(cmd_Id, Client, Data)    cmd_id is pimary key produit(pro_Id,libelle)   pro_id is primary key ligneCmd(Cmd_Id,pro_id)    pro_id and cmd id are primary keys and foreign keys help me pleaze thank's

• Anonymous
  May 26, 2012
  How do you handle if you have another collumn in the association table(ProjectEmps), for exp : project assined date, You microsofts guys should come up with real and complex problem not chota problems like above. Regards, Ashwatha

• Anonymous
  April 04, 2014
  Can you tell me if i want to add an extra field in ProjectEmps table how can i do that!