首先与代码建立多对多关系的Map View

Question

There is an issue am struggling with for a while. This is the only post I found that describes similar problem post1 , but it doesn't solves mine.

I am using a EF6.1 code first for my app and need to add a view and define many-to-many relationship for it.

Consider this:

public class Employee
{
    public int EmployeeId { get; set; }

    public int EmployeeName { get; set; }

    ICollection<Location> Locations {get; set;}
}

public class Location
{
    public int LocId { get; set; }

    public int LocName { get; set; }
}

in model builder OnModelCreating:

            modelBuilder.Entity<Employee>().HasMany<Location>(t => t.Locations)
            .WithMany().Map(mc =>
            {
                mc.ToTable("EmployeeLocations");
                mc.MapLeftKey("EmployeeId");
                mc.MapRightKey("LocId");
            });

In db I get a mapping table EmployeeLocations and everything works fine.

Now I want to add a view - sort of an employee extension. I've got this view in the DB and related paco class:

      public class Employee
{
    public int EmployeeId { get; set; }

    public int EmployeeName { get; set; }

     public string SomeOtherProp {get; set;}
    ICollection<Location> Locations {get; set;}
}

I've added a DbSet for it and this configuration: this.HasKey(e => e.EmployeeID); this.ToTable("EmployeeLocations ");

It populates fine and I am able to query it, but without the Locations - it is always empty.

does any one knows how can I define this many-to-many relationship?

Answer 1

Going by your models, you're not loading related entities (Locations). You'll need to mark the collection as virtual to populate it automatically (lazy loading):

public virtual ICollection<Location> Locations {get; set;}

Or explicitly by adding .Include(e => e.Locations) in your queries (You'll need to add the namespace System.Data.Entity for it work):

var employeeItem = context.Employee.Include(e => e.Locations).FirstOrDefault(x => x.EmployeeName == "Bob");

Hope that helps!