Blazorise DataGrid: Observable Data

@code {
    private ObservableCollection<Employee> items = new() {
        new() { FirstName = "Name 1" },
        new() { FirstName = "Name 2" }
    };

    private Task OnAddItemClick()
    {
        items.Add( new Employee { FirstName = $"Name {items.Count + 1}" } );

        return Task.CompletedTask;
    }

    private Task OnRemoveItemClick()
    {
        if ( items.Count > 0 )
            items.RemoveAt( 0 );

        return Task.CompletedTask;
    }


    public class Gender
    {
        public string Code { get; set; }
        public string Description { get; set; }
    }

    public class EmployeeData
    {
        private static readonly string[] FirstNames = ["Samuel", "Irvin", "Cora", "Jessie", "Maryann", "Kara"];
        private static readonly string[] LastNames = ["Collier", "Ziemann", "Conn", "Wilkinson", "Hilpert", "Brekke"];
        private static readonly string[] Cities = ["London", "Paris", "New York", "Berlin", "Lisbon", "Zagreb"];

        public static IEnumerable<Gender> Genders =
        [
            new() { Code = null, Description = string.Empty },
            new() { Code = "M", Description = "Male" },
            new() { Code = "F", Description = "Female" },
            new() { Code = "D", Description = "Diverse" }
        ];

        public Task<List<Employee>> GetDataAsync()
            => Task.FromResult( Enumerable.Range( 1, 500 )
                .Select( index =>
                {
                    string firstName = FirstNames[( index - 1 ) % FirstNames.Length];
                    string lastName = LastNames[( index - 1 ) % LastNames.Length];

                    return new Employee
                    {
                        Id = index,
                        FirstName = firstName,
                        LastName = lastName,
                        Email = $"{firstName}.{lastName}{index}@example.com",
                        City = Cities[( index - 1 ) % Cities.Length],
                        Zip = $"{10000 + index}",
                        DateOfBirth = new DateTime( 1950 + index % 50, 1 + index % 12, 1 + index % 28 ),
                        Childrens = index % 6,
                        Gender = index % 3 == 0 ? "D" : index % 2 == 0 ? "F" : "M",
                        Salary = 50000m + index * 137m % 50000m,
                        IsActive = index % 2 == 0,
                        Salaries = Enumerable.Range( 1, index % 4 )
                            .Select( month => new Salary
                            {
                                Date = new DateTime( 2025, month, 1 ),
                                Total = 1000m + index * month * 11m
                            } )
                            .ToList()
                    };
                } )
                .ToList() );
    }

    public class Employee
    {
        public Employee()
        {
        }

        public Employee( Employee other )
        {
            Id = other.Id;
            Childrens = other.Childrens;
            DateOfBirth = other.DateOfBirth;
            City = other.City;
            Email = other.Email;
            FirstName = other.FirstName;
            LastName = other.LastName;
            Gender = other.Gender;
            IsActive = other.IsActive;
            Salaries = other.Salaries;
            Salary = other.Salary;
            Tax = other.Tax;
            Zip = other.Zip;
        }

        [Display( Name = "Id" )]
        public int Id { get; set; }

        [Required]
        public string FirstName { get; set; }

        [Required]
        public string LastName { get; set; }

        [Required]
        [EmailAddress]
        [Display( Name = "Email" )]
        public string Email { get; set; }

        [Display( Name = "City" )]
        public string City { get; set; }

        [Display( Name = "Zip" )]
        public string Zip { get; set; }

        [Display( Name = "DOB" )]
        public DateTime? DateOfBirth { get; set; }

        [Display( Name = "Childrens" )]
        public int? Childrens { get; set; }

        [Display( Name = "Gender" )]
        public string Gender { get; set; }

        [Display( Name = "Salary" )]
        public decimal Salary { get; set; }

        [Display( Name = "Tax" )]
        public decimal Tax
        {
            get
            {
                if ( tax == 0 && Salary > 0 )
                {
                    tax = Salary * TaxPercentage;
                }

                return tax;
            }
            set
            {
                tax = value;
            }
        }

        [Display( Name = "Active" )]
        public bool IsActive { get; set; }

        public List<Salary> Salaries { get; set; } = new();

        public decimal ChildrensPerSalary
            => Salary == 0m
                ? 0m
                : ( Childrens is null || Childrens == 0 ? 1 : Childrens.Value ) / Salary;

        public decimal TaxPercentage = 0.25m;

        private decimal tax;
    }

    public class Salary
    {
        public DateTime Date { get; set; }
        public decimal Total { get; set; }
    }
}