Question

I have 2 classes Bill and BillType. Each Bill should have a BillType and TypeId should be a FK. Using Code First, a column is added to my database table Bills called BillType_TypeId that has a FK relationship with the table BillTypes.

public class Bill
{
    [Key]
    public int BillId { get; set; }

    [Required, MaxLength(100)]
    public string Name { get; set; }

    [Required]
    public decimal Amount { get; set; }

    public System.DateTime DueDate { get; set; }

    [Required]
    public Guid UserId { get; set; }
}

public class BillType
{
    [Key]
    public int TypeId { get; set; }

    [Required, MaxLength(100)]
    public string Name { get; set; }

    public virtual List<Bill> Bills { get; set; }
}

My problem comes when I need to insert a TypeId into the Bills table. I’ve been using this code to insert:

public class BillActions
{
    private BillContext _db = new BillContext();

    public Boolean InsertNewBill(int billType, string name, decimal amount, DateTime dueDate, Guid userId)
    {
        var bill = new Bill {                
            xxx                              <-- problem is here
            Name = name,
            Amount = amount,
            DueDate = dueDate,
            UserId = userId 
        };

        _db.Bills.Add(bill);

        _db.SaveChanges();
        return true;
    }
}

There isn’t an exposed object make equal to int billType. I’m not sure how to add it while still maintaining the FK constraints. How do I accomplish this. Also, I’m using Entity Framework 5.

Answer 1

You could update your class to expose the BillType reference:

public class Bill
{
    [Key]
    public int BillId { get; set; }

    [Required, MaxLength(100)]
    public string Name { get; set; }

    [Required]
    public decimal Amount { get; set; }

    public System.DateTime DueDate { get; set; }

    [Required]
    public Guid UserId { get; set; }

    public int BillTypeId {get;set;}
    public BillType BillType {get;set;}
}

then your create:

    var bill = new Bill {                
        BillTypeId = billType,
        Name = name,
        Amount = amount,
        DueDate = dueDate,
        UserId = userId 
    };

If you don’t want to expose the reference of the BillType on the bill, you could also add a fluent mapping:

        modelBuilder.Entity<BillType>()
            .HasMany(bt => bt.Bills)
            .WithOptional()
            .HasForeignKey(bt => bt.BillTypeId);