数据库优先方法的唯一约束

Question

I'm have database with many unique constraints.

I'm aware of that entity framework doesn't know anything about them. So I need to add them to the model manually. But in

System.ComponentModel.DataAnnotations

There is no Unique keyword.

I created new attribute:

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
public class UniqueKeyAttribute : Attribute
{
}

and added it to my model:

[MetadataType(typeof(DeviceInstance))]
public partial class DeviceInstance
{
    public int Id { get; set; }
    [Required]
    public int DeviceId { get; set; }
    [Required]
    [UniqueKey]
    [MaxLength(50)]
    public string SerialNo { get; set; }
    [Required]
    public System.DateTime CreationDate { get; set; }
}

Even that Model.IsValid is always returning true even if there is already that value in the table.

What code should I write to change this behavior?

Answer 1

A simple answer to your question is that Entity framework doesn't support unique keys so the only way is to set the unique constraint is in in the database (as you in fact did). By doing so appropriate exceptions will be thrown when you try to insert/update new rows in the DB in case of a lack of uniqueness, which you can then catch and handle.