enitity framework relation one - to - many มัน error ครับ

[Table("users")]
    public class Users
    {
        [Key]
        public int userID { get; set; }

        public int? employeeID { get; set; }

        [StringLength(50)]
        public string employeeCode { get; set; }

        [StringLength(50)]
        public string firstname { get; set; }

        [StringLength(50)]
        public string middlename { get; set; }

        [StringLength(50)]
        public string lastname { get; set; }

        [StringLength(50)]
        public string nickname { get; set; }

        [StringLength(50)]
        public string email { get; set; }

        [StringLength(50)]
        public string password { get; set; }

        public virtual ICollection<Question> Questions { get; set; }
    }

[Table("question")]
    public class Question
    {
        [Key]
        public int questionID { get; set; }

        public string year { set; get; }
        
        [StringLength(50)]
        public string code { get; set; }
    
        [Column(TypeName = "text")]
        public string topic { get; set; }
        
        [Column(TypeName = "text")]
        public string description { get; set; }

        public int? status { get; set; }

        public int createdID { get; set; }

        [DataType(DataType.Date)]
        public DateTime createdDate { get; set; }
        
        public virtual Users user { get; set; }
    }