Creating unique filtered index using code first in Entity Framework 6

I came across a requirement last week where users can associate additional email addresses to their account. Users will then have to confirm their additional email addresses. I added a new table in the database to accommodate this requirement. The table contains a PersonId column which is a foreign key to the Person table, an EmailAddress and EmailConfirmed columns.

I needed to create a unique filtered index on EmailAddress column where the email is confirmed. In Entity Framework 6, you can create an index for a column or across multiple columns by using the [Index] attribute.

i.e Single column index

public class Location
{
    public int Id { get; set; }

    [Index]
    public string Code { get; set; }
    public int Name { get; set; }
}

..or multiple columns index

public class Location
{
    public int Id { get; set; }

    [Index("CodeAndName", 1, IsUnique = true)]
    public string Code { get; set; }

    [Index("CodeAndName", 2)]
    public int Name { get; set; }
}

However, Entity Framework 6 does not support filtered index using the [Index] attribute. It has to be added manually during database migration. In my scenario, in the database migration file after executing add-migration, I would have to run a Sql script in the Up() method after the CreateTable to add the index and in Down() method to drop the index.

public partial class AddEmailAssociations : DbMigration
{
    /// <inheritdoc />
    public override void Up()
    {
        this.CreateTable(
            "dbo.EmailAssociation",
            c => new
                {
                    Email = c.String(nullable: false, maxLength: 150),
                    PersonId = c.String(nullable: false, maxLength: 128),
                    EmailConfirmed = c.Boolean(nullable: false),
                })
            .PrimaryKey(t => new { t.Email, t.PersonId })
            .ForeignKey("dbo.Person", t => t.PersonId, cascadeDelete: true)
            .Index(t => t.PersonId);
            
        this.Sql("create unique nonclustered index IX_EmailAssociation_Email on dbo.EmailAssociation(Email) where EmailConfirmed = 1");
    }

    /// <inheritdoc />
    public override void Down()
    {
        this.DropForeignKey("dbo.EmailAssociation", "PersonId", "dbo.Person");
        this.DropIndex("dbo.EmailAssociation", new[] { "PersonId" });
        this.DropIndex("dbo.EmailAssociation", "IX_EmailAssociation_Email");
        this.DropTable("dbo.EmailAssociation");
    }
}