Access to Many-to-Many table

Question

I have two tables, Project and BOM . Their relationship is many-to-many .

When I check my Migration class, I can see the below code that was automatically generated.

CreateTable(
    "dbo.ProjectBOMs",
    c => new
        {
            Project_Id = c.Int(nullable: false),
            BOM_Id = c.Int(nullable: false),
        })
    .PrimaryKey(t => new { t.Project_Id, t.BOM_Id })
    .ForeignKey("dbo.Projects", t => t.Project_Id, cascadeDelete: true)
    .ForeignKey("dbo.BOMs", t => t.BOM_Id, cascadeDelete: true)
    .Index(t => t.Project_Id)
    .Index(t => t.BOM_Id);

However, when I try to access this table using the following method, it's not showing up.

using(var db = new ApplicationDbContext())
{
    db.ProjectBOMs //<== there's no ProjectBOMs in db
}

Since ProjectBOMs table has already been automatically generated, do I have to write the following code again to be able to access the table?

modelBuilder.Entity<Project>()
    .HasMany<BOM>(x => x.BOMs)
    .WithMany(x => x.Projects)
    .Map(x =>
    {
        x.MapLeftKey("Project_Id");
        x.MapRightKey("BOM_Id");
        x.ToTable("ProjectBOMs");
    });

Answer 1

I think the issue might be that the table isn't an entity in itself in your model, it's just the result of how the many-many relationship between Project and BOM is represented in a SQL database (ie with a joining table).

Do you need to access it because you need additional columns in the table? If so this question and the top voted answer look pretty useful.

Answer 2

The if the table ProjectBOMs consists only of the Forign Key columns to Projects and BOMs then the table is NOT imported. It will result in a Project Collection on the BOMS and a BOM Collection on Projects, but will not be available as a stand alone entity.