Entity Framework - Fluent API - Creating Weird Columns PK : FK FK

Question

My project is Database First and I'm using Entity Framework 6.2.0.

So I have following classes in simple illustration:

Person [1]    [n] Link_Table [n]    [1] Area
======            ==========            ====
ID                ID                    ID 
                  PersonID (FK)         
                  AreaID (FK)

Now when using following code it will through me an inner exception of "invalid column name 'Area2_ID'".

Db_Context db = new Db_Context();

// getting all links with specific "personID"
List<Link_Table> links = db.Link_Table.Where(item => item.PersonID == personID).ToList();

// now getting all areas
List<Area> areas= new List<Area>();
foreach (Link_Table link in links)
{
    // ERROR
    areas.Add(db.Area.Where(item => item.ID == link.areaID).First());
}

I've already read a little bit about this problem by another users and the problem should be in the (auto-generated) OnModelCreating .

modelBuilder.Entity<Area>()
            .Property(e => e.Description)
            .IsUnicode(false);

        modelBuilder.Entity<Area>()
            .HasOptional(e => e.Area1)
            .WithRequired(e => e.Area2);

For whatever reason using EF in code and creating a new Area-Object, it will show me not only "ID"-Property, but also "Area1"- and "Area2"-Property.

Question How i have to handle it? The columns "Area1_ID" and "Area2_ID" only exist in EF, not in the database. Can I remove these properties or something else to prevent my exception?

EDIT: My models:

[Table("Area")]
public partial class Area
{
    public Guid ID { get; set; }

    [StringLength(40)]
    public string Name { get; set; }

    [Column(TypeName = "text")]
    public string Description{ get; set; }

    public virtual Area Area1 { get; set; }

    public virtual Area Area2 { get; set; }
}

public partial class Link_Table
{
    public Guid ID { get; set; }

    public Guid? Person_ID { get; set; }

    public Guid? Area_ID { get; set; }

    public virtual Person Person{ get; set; }
}

[Table("Person")]
public partial class Person
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public Person()
    {
        Link_Table = new HashSet<Link_Table>();
    }

    public Guid ID { get; set; }
}

Answer 1

This line looks suspect:

areas.Add(db.Area.Where(item => item.ID == link.areaID).First());

item.ID is the index of the link table record, not an area record.

areas.Add(db.Area.Where(item => item.AreaID == link.areaID).First());

Answer 2

Not very clear for me your goal, but you can refactor your code as follow:

this code:

// now getting all areas
List<Area> areas= new List<Area>();
foreach (Link_Table link in links)
{
    // ERROR
    areas.Add(db.Area.Where(item => item.ID == link.areaID).First());
}

can be replaced with:

var areas=links.Select(link => link.Area).ToList() // if you decide to add a navigation property

or

var areas=db.Areas.Where(area => links?.Any(link=>link.areaID==area.Id)).ToList();

Most problably the error you get was from .First() for the future use .FirstOrDefault()

Please see below an example of code first implementation:

class Program
{
    static void Main(string[] args)
    {
        var db = new ApplicationDbContext();
        var person = new Person();
        IQueryable<Link> personLinks = db.Links.Where(x => x.PersonId == person.Id);
        List<Area> personAreas = personLinks.GroupBy(x => x.Area).Select(x => x.Key).ToList(); 
    }
}

public class Person
{
    public int Id { get; set; }
    public ICollection<Link> Links { get; set; }
}

public class Link
{
    public int Id { get; set; }
    public int PersonId { get; set; }
    public Person Person { get; set; }
    public int AreaId { get; set; }
    public Area Area { get; set; }
}

public class Area
{
    public int Id { get; set; }
    public ICollection<Link> Links { get; set; }
}

public class ApplicationDbContext : DbContext
{
    public DbSet<Person> Persons { get; set; }
    public DbSet<Area> Areas { get; set; }
    public DbSet<Link> Links { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Link>()
            .HasRequired(x => x.Person)
            .WithMany(x => x.Links)
            .HasForeignKey(x => x.PersonId)
            .WillCascadeOnDelete(true);

        modelBuilder.Entity<Link>()
            .HasRequired(x => x.Area)
            .WithMany(x => x.Links)
            .HasForeignKey(x => x.AreaId)
            .WillCascadeOnDelete(false);

        base.OnModelCreating(modelBuilder);
    }
}

here you can lear more about entity framework code first follow this link

Answer 3

When was the last time you ran a database migration? If your model is correct, and your database is saying there are missing fields, then the database doesn't match the code.