Entity Framework, Technical

Creating a composite primary keys in Entity Framework 4.1

There are two main ways of achieving this. Let’s look at an object – Brochure: { ProductId, Year, Month, ProductName}. We want:

  • ProductId
  • Year
  • Month

To make up the primary key.

Method 1 – Data annotations

In your entity class, simply decorate any properties that you want to make up your key with the attribute “Key”:

public class Brochure
    [Key, Column(Order = 0)]
    public int ProductId { get; set; }

    [Key, Column(Order = 1)]
    public int Year { get; set; }

    [Key, Column(Order = 3)]
    public int Month { get; set; }

    public string ProductName { get; set; }

Method 2 – DbMigration class

NOTE: You shouldn’t need to use this method if you are using full entity framework code first. However, some projects only use entity framework to handle migrations – so this might be of use to you:

public partial class BrochureTable : DbMigration
 public override void Up()
 CreateTable("Brochures", c => new
 ProductId = c.Int(nullable: false),
 Year = c.Int(nullable: false),
 Month = c.Int(nullable: false),
 ProductName = c.String(maxLength: 60)
 .PrimaryKey(bu => new {bu.ProductId, bu.Year, bu.Month});


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