public override string ToString()
        {
            var sb = new StringBuilder();

            sb.Append($"Student[{ID}] ")
            .Append($"{User.FirstName} {User.LastName} | ")
            .Append($"DOB: {(DateOfBirth != null ? ((DateTime)DateOfBirth).ToString("yyyy/MM/dd") + " | " : "N/A | ")}")
            .Append($"Tuition fees: {(TuitionFees != null ? TuitionFees.ToString() : "N/A")}");
            return(sb.ToString());
        }
 public override string ToString()
 {
     return(String.Format("{0, -11} {1, -22} {2, -32} {3, -15} {4, -14}", StudentId,
                          FirstName, LastName, DateOfBirth.ToString("dd'/'MM'/'yyyy"), TuitionFees.ToString("F")));
 }