[Flags]
public enum Gender : byte
{
     None=0, Male=1, Female=2,
};

public class User
{
    public int UserId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Username { get; set; }

    [Column(Name="Gender")]
    public int InternalGender { get; set; }
    [NotMapped]
    public Gender Gender
    {
        get { return (Gender)this.InternalGender; }
        set { this.InternalGender = (int)value; }
    }

    public DateTime DateOfBirth { get; set; }
}

 modelBuilder.Entity<Participant>().Ignore(p => p.Gender);
 modelBuilder.Entity<Participant>().Property(p => p.InternalGender).HasColumnName("Gender");