public class UserDetail
    {
        [Key]
        public int UserId { get; set; }

        public int? ImageId { get; set; }
        public virtual Image Image { get; set; }
    }

    public class Image : BaseEntity
    {
        public string Img { get; set; }
        public virtual ICollection<UserDetail> UserDetails { get; set; }

        [Index(IsUnique = true)]
        public long? ImageKey { get; set; }
    }

public class UserDetail
    {
        [Key]
        public int UserId { get; set; }

        public int? ImageId { get; set; }
        public virtual Image Image { get; set; }
        [NotMapped]
        public long? ImageKey => Image.ImageKey;