How to define a table that its primary key is constructed from 2 foreign keys with EF code-first

lobengula3rd Published at Dev

lobengula3rd

I am using models to define my tables using EF code-first.

I have and Item model and an Order model.

Item:

 public class Item
    {
        public int ItemID { get; set; }

        [Required]
        public int Price { get; set; }

        [Required]
        public int AmountLeft { get; set; }

        [Required]
        public string Image { get; set; }

        [Required]
        public string Description { get; set; }

        [Required]
        public string FullDescription { get; set; }

        [Required]
        public DateTime PublishDate { get; set; }


        public int CompanyID { get; set; }
        public int CategoryID { get; set; }

        // Navigation properties 
        public virtual Company Company { get; set; }

        // Navigation properties 
        public virtual Category Category { get; set; } 

    }

Order model:

public class Order
    {
        public int OrderID { get; set; }

        [Required]
        public DateTime DeliveryDate { get; set; }

        [Required]
        public string Currency { get; set; }

        [Required]
        public int TotalAmount { get; set; }

        public List<int> Items { get; set; }


        public DateTime OrderDate { get; set; }


        public int UserID { get; set; }
        // Navigation properties 
        public virtual User user { get; set; }

    }

I want to create another table which will be called ItemInOrder which will only have 2 fields: ItemID and OrderID. the primary key would be these 2 foreign keys.

i tried to define this model:

   public class ItemInOrder
    {

        public int OrderID { get; set; }
        public int ItemID { get; set; }

        // Navigation properties 
        public virtual Order order { get; set; }
        public virtual Item item { get; set; }

    }

But i got errors. i tried to put [Key] notation on both fields but still i got errors.

how will i be able to create the table i want?

octavioccl

When you need to create a table with composite PKs, you need to specify the order of you keys. There are two variants:

You could override the OnModelCreating method on your Context, and try with these Fluent Api configurations:

// Configure the primary keys for the ItemInOrder in the order you want
modelBuilder.Entity<ItemInOrder>() 
    .HasKey(t => new{t.OrderID,ItemID); 

modelBuilder.Entity<ItemInOrder>() 
            .HasRequired(io=>io.Order)
            .WithMany()
            .HasForeigKey(io=>io.OrderID);

 modelBuilder.Entity<ItemInOrder>() 
           .HasRequired(io=>io.Item)
           .WithMany()
           .HasForeigKey(io=>io.ItemID);

The second variant using Data Annotations should be this way:

[Key] 
[Column(Order=1)] 
[ForeignKey("Order")]
public int OrderID { get; set; }

[Key] 
[Column(Order=2)] 
[ForeignKey("Item")]
public int ItemID { get; set; }

EF will notice you want to create two relationships and it will do the job for you.

Collected from the Internet

Please contact [email protected] to delete if infringement.