Composite Key with EF 4.1 Code First

I am trying to figure out how to have a composite key using EF code First 4.1 RC.

Currently, I am using the [Key] Data Annotation, but I am unable to specify more than one key.

how would one specify a composite key?

Here is my Example:

 public class ActivityType
{
    [Key]
    public int ActivityID { get; set; }

    [Required(ErrorMessage = "A ActivityName is required")]
    [StringLength(50, ErrorMessage = "Activity Name must not exceed 50 characters")]
    public string ActivityName { get; set; }

}

I need the "ActivityName" to also be a key. Sure, I can code around this, but thats not good database design.

---

You can mark both ActivityID and ActivityName properties with Key annotation or you can use fluent API as described by @taylonr.

Edit:

This should work - composite key defined with annotations requires explicit column order:

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

    [Key, Column(Order = 1)]
    [Required(ErrorMessage = "A ActivityName is required")]
    [StringLength(50, ErrorMessage = "Activity Name must not exceed 50 characters")]
    public string ActivityName { get; set; }

}

---

我们不使用注释，而是重写模型构建器，在这种情况下，您可以执行如下操作：

modelBuilder.Entity<Activity>().HasKey(a => new { a.ActivityId, a.ActivityName });

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