Blazorise DataGrid: Large Data

@code {
    [Inject]
    public EmployeeData EmployeeData { get; set; }
    private List<Employee> employeeList;
    private string oDataQuery;
    protected override async Task OnInitializedAsync()
    {
        employeeList = await EmployeeData.GetDataAsync();
        await base.OnInitializedAsync();
    }

    private int totalEmployees;

    private async Task OnReadData( DataGridReadDataEventArgs<Employee> e )
    {
        oDataQuery = e.ToODataString( "https://services.odata.org/V4/Northwind/Northwind.svc/Employees" );

        if ( !e.CancellationToken.IsCancellationRequested )
        {
            List<Employee> response = null;

            // this can be call to anything, in this case we're calling a fictional api
            //var response = await Http.GetJsonAsync<Employee[]>( $"some-api/employees?page={e.Page}&pageSize={e.PageSize}" );
            if ( e.ReadDataMode is DataGridReadDataMode.Virtualize )
                response = ( await EmployeeData.GetDataAsync() ).Skip( e.VirtualizeOffset ).Take( e.VirtualizeCount ).ToList();
            else if ( e.ReadDataMode is DataGridReadDataMode.Paging )
                response = ( await EmployeeData.GetDataAsync() ).Skip( ( e.Page - 1 ) * e.PageSize ).Take( e.PageSize ).ToList();
            else
                throw new Exception( "Unhandled ReadDataMode" );

            if ( !e.CancellationToken.IsCancellationRequested )
            {
                totalEmployees = ( await EmployeeData.GetDataAsync() ).Count;
                employeeList = new List<Employee>( response ); // an actual data for the current page
            }
        }
    }
}

@code {
    [Inject] public EmployeeData EmployeeData { get; set; }
    private DataGrid<Employee> dataGridRef;
    private List<Employee> employeeListSource;
    private List<Employee> employeeList;

    protected override async Task OnInitializedAsync()
    {
        employeeListSource = await EmployeeData.GetDataAsync();
        await base.OnInitializedAsync();
    }

    private int totalEmployees;

    private async Task OnReadData(DataGridReadDataEventArgs<Employee> e)
    {

        if (!e.CancellationToken.IsCancellationRequested)
        {
            var query = employeeListSource.AsQueryable().ApplyDataGridSort(e.Columns).ApplyDataGridSearch(e.Columns);

            if (dataGridRef.CustomFilter is not null)
                query = query.Where(item => item != null && dataGridRef.CustomFilter(item));

            var response = new List<Employee>();

            if (e.ReadDataMode is DataGridReadDataMode.Virtualize)
                response = query.ApplyDataGridPaging(e.VirtualizeOffset + 1, e.VirtualizeCount).ToList();
            else if (e.ReadDataMode is DataGridReadDataMode.Paging)
                response = query.ApplyDataGridPaging(e.Page, e.PageSize).ToList();
            else
                throw new Exception("Unhandled ReadDataMode");

            await Task.Delay(Random.Shared.Next(100));

            if (!e.CancellationToken.IsCancellationRequested)
            {
                totalEmployees = query.Count();
                employeeList = response;
            }
        }
    }
}