@inject IWebHostEnvironment HostingEnvironment

<TelerikGrid Data="@bookList" Height="75svh" Resizable="true" Sortable="true" Pageable="true" PageSize="15"
             FilterMode="@GridFilterMode.FilterMenu" SelectionMode="@GridSelectionMode.Multiple"
             SelectedItems="@SelectedBooks" @ref="@BookGrid"
             SelectedItemsChanged="@((IEnumerable<BookInfo> sel) => OnRowSelect(sel))">
    <GridToolBarTemplate>
        <TelerikButton OnClick="@GenerateReport">Generate PDF</TelerikButton>
    </GridToolBarTemplate>
    <GridExport>
        <GridPdfExport AllPages="true" PageOrientation="GridPdfExportPageOrientation.Landscape"
                       PaperSize="GridPdfExportPaperSize.A3" />
    </GridExport>
    <GridColumns>
        <GridCheckboxColumn CheckBoxOnlySelection="true"></GridCheckboxColumn>
        <GridColumn Field="ISBN">
            <HeaderTemplate><b>ISBN</b></HeaderTemplate>
        </GridColumn>
        <GridColumn Field="Author">
            <HeaderTemplate><b>Author</b></HeaderTemplate>
        </GridColumn>
        <GridColumn Field="Title">
            <HeaderTemplate><b>Title</b></HeaderTemplate>
        </GridColumn>
        <GridColumn Field="Genre">
            <HeaderTemplate><b>Genre</b></HeaderTemplate>
        </GridColumn>
        <GridColumn Field="PublishedYear">
            <HeaderTemplate><b>Year</b></HeaderTemplate>
        </GridColumn>
        <GridColumn Field="CopiesAvailable">
            <HeaderTemplate><b>Copies</b></HeaderTemplate>
        </GridColumn>
    </GridColumns>
</TelerikGrid>

@code {
    private async Task GenerateReport()
    {
        isLoading = true;
        var pdfStream = await BookGrid.ExportToPdfAsync();

        // The stream is actually XLSX, so convert it to PDF
        using var ms = new MemoryStream(pdfStream.ToArray());

        var xlsxProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.XlsxFormatProvider();
        var workbook = xlsxProvider.Import(ms);

        var rootPath = HostingEnvironment.WebRootPath;
        var saveLocation = Path.Combine(rootPath, "LibraryBooks.pdf");
        var pdfProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.Pdf.PdfFormatProvider();
        using (var fileStream = new FileStream(saveLocation, FileMode.Create))
        {
            pdfProvider.Export(workbook, fileStream);
        }
    }

    public class BookInfo
    {
        public string ISBN { get; set; }
        public string Author { get; set; }
        public string Title { get; set; }
        public string Genre { get; set; }
        public int PublishedYear { get; set; }
        public int CopiesAvailable { get; set; }
    }

    private List<BookInfo> bookList = new()
    {
        new BookInfo { ISBN = "978-0451524935", Author = "George Orwell", Title = "1984", Genre = "Dystopian", PublishedYear = 1949, CopiesAvailable = 4 },
        new BookInfo { ISBN = "978-0439139601", Author = "J.K. Rowling", Title = "Harry Potter and the Goblet of Fire", Genre = "Fantasy", PublishedYear = 2000, CopiesAvailable = 7 },
        new BookInfo { ISBN = "978-0140449266", Author = "Homer", Title = "The Odyssey", Genre = "Epic Poetry", PublishedYear = -800, CopiesAvailable = 2 }
    };

    private TelerikGrid<BookInfo> BookGrid;
    private List<BookInfo> SelectedBooks = new();
    private bool isLoading = false;

    private void OnRowSelect(IEnumerable<BookInfo> selected)
    {
        SelectedBooks = selected.ToList();
    }
}

<TelerikGrid Data="@GridData"
             SelectionMode="@GridSelectionMode.Multiple"
             SelectedItems="@SelectedItems"
             SelectedItemsChanged="@( (IEnumerable<Employee> newSelected) => OnSelectedItemsChanged(newSelected) )"
             Height="300px">
    <GridToolBarTemplate>
        <TelerikButton Enabled="@(SelectedItems.Any())" OnClick="@DeleteSelectedEmployees">Delete</TelerikButton>
    </GridToolBarTemplate>
    <GridColumns>
        <GridCheckboxColumn SelectAll="true" />
        <GridColumn Field="Name" Title="Name" />
        <GridColumn Field="Team" Title="Team" />
    </GridColumns>
</TelerikGrid>

@code {
    private List<Employee> GridData { get; set; } = Enumerable.Range(1, 10).Select(i => new Employee
    {
        EmployeeId = i,
        Name = $"Employee {i}",
        Team = $"Team {i % 3}"
    }).ToList();

    private List<Employee> SelectedItems { get; set; } = new();

    private void OnSelectedItemsChanged(IEnumerable<Employee> items)
    {
        SelectedItems = items.ToList();
    }

    private void DeleteSelectedEmployees()
    {
        if (SelectedItems.Any())
        {
            GridData = GridData.Except(SelectedItems).ToList();
            SelectedItems.Clear();
        }
    }

    public class Employee
    {
        public int EmployeeId { get; set; }
        public string Name { get; set; }
        public string Team { get; set; }
        public override bool Equals(object obj) => obj is Employee e && e.EmployeeId == EmployeeId;
        public override int GetHashCode() => EmployeeId.GetHashCode();
    }
}

@using Telerik.Blazor.Components.Grid

@inject IJSRuntime JS

<PageTitle>Home</PageTitle>

<TelerikGrid Data="@GridData">
    <GridToolBarTemplate>
        <TelerikButton OnClick="@ExportGridWithOtherColumns">Export Programmatically</TelerikButton>
        <GridCommandButton Class="hidden-export-button" Command="ExcelExport">Export Natively</GridCommandButton>
    </GridToolBarTemplate>
    <GridSettings>
        <GridExcelExport OnBeforeExport="@OnGridBeforeExport" />
    </GridSettings>
    <GridColumns>
        <GridColumn Field="@nameof(Product.Id)" Width="100px" />
        <GridColumn Field="@nameof(Product.Name)" Width="120px" />
        <GridColumn Title="Product Details">
            <Columns>
                <GridColumn Field="@nameof(Product.Group)" Width="180px" />
                <GridColumn Field="@nameof(Product.Price)" DisplayFormat="{0:c2}" Width="120px" />
                <GridColumn Field="@nameof(Product.Quantity)" DisplayFormat="{0:n0}" Width="120px" />
                <GridColumn Field="@nameof(Product.Released)" DisplayFormat="{0:d}" Width="180px" />
                <GridColumn Field="@nameof(Product.Discontinued)" Width="100px" />
            </Columns>
        </GridColumn>
    </GridColumns>
</TelerikGrid>

<style>
    .hidden-export-button {
        display: none;
    }
</style>

<script suppress-error="BL9992">
    function clickExportCommandButton() {
        let hiddenExportButton = document.querySelector(".hidden-export-button");
        if (hiddenExportButton) {
            hiddenExportButton.click();
        }
    }
</script>

@code {
    private List<Product> GridData { get; set; } = new();

    private void OnGridBeforeExport(GridBeforeExcelExportEventArgs args)
    {
        List<string> exportableColumnFields = new List<string> { nameof(Product.Name), nameof(Product.Price), nameof(Product.Quantity) };
        List<GridExcelExportColumn> ColumnsToExport = new();

        foreach (GridExcelExportColumn column in args.Columns)
        {
            if (exportableColumnFields.Contains(column.Field))
            {
                ColumnsToExport.Add(column);
            }
        }

        args.Columns = ColumnsToExport;
    }

    private async Task ExportGridWithOtherColumns()
    {
        await JS.InvokeVoidAsync("clickExportCommandButton");
    }

    protected override void OnInitialized()
    {
        var rnd = Random.Shared;

        for (int i = 1; i <= 7; i++)
        {
            GridData.Add(new Product()
            {
                Id = i,
                Name = $"Name {i} {(char)rnd.Next(65, 91)}{(char)rnd.Next(65, 91)}",
                Group = $"Group {i % 3 + 1}",
                Price = rnd.Next(1, 100) * 1.23m,
                Quantity = rnd.Next(0, 10000),
                Released = DateTime.Today.AddDays(-rnd.Next(60, 1000)),
                Discontinued = i % 4 == 0
            });
        }
    }

    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; } = string.Empty;
        public string Group { get; set; } = string.Empty;
        public decimal Price { get; set; }
        public int Quantity { get; set; }
        public DateTime Released { get; set; }
        public bool Discontinued { get; set; }
    }
}

The TelerikGrid never loads any data. the app just hangs. 

I copied the Telerik sample from the online demo. 

 The HTML table loads perfectly.

 Using VS 2019  16.1.0 Preview 2.0.

Acquired Telerik nuget package directly from Telerik feed.

    <TelerikGrid Data=@ViewModel.GetCorePharmacies() Height="300">
        <TelerikGridColumns>
            <TelerikGridColumn Field="ID" Title="NCPDP#" />
            <TelerikGridColumn Field="NPINumber" Title="NPI#" />
            <TelerikGridColumn Field="DBAName" Title="Pharmacy" />
            <TelerikGridColumn Field="StoreNumber" Title="Store#" />
        </TelerikGridColumns>
    </TelerikGrid>

    @*<table class="table">
        <thead>
            <tr>
                <th>NCPDP</th>
                <th>NPI</th>
                <th>DBA Name</th>
                <th>Store#</th>
            </tr>
        </thead>
        <tbody>
            @foreach (var pharmacy in ViewModel.GetCorePharmacies())
            {
                <tr>
                    <td>@pharmacy.ID.ToString()</td>
                    <td>@pharmacy.NPINumber.ToString()</td>
                    <td>@pharmacy.DBAName</td>
                    <td>@pharmacy.StoreNumber</td>
                </tr>
            }
        </tbody>
    </table>*@

Any thoughts. 

<button @onclick="@MyClick">Add item</button>

void MyClick()
{
    MyData.Add(new SampleData() { ID = 46, Name = "from click" });
    StateHasChanged();
}

@using ClientApp.Shared
@inject HttpClient Http

<TelerikGrid Data=@forecasts Height="550px"
                Pageable="true" Sortable="true"
                PageSize="20" Groupable="true">
    <GridColumns>
        <GridColumn Field="Date">
            <Template>
                @((context as WeatherForecast).Date.ToString("dddd, dd MMM yyyy"))
            </Template>
        </GridColumn>
        <GridColumn Field="TemperatureC" Title="Temp. C" />
        <GridColumn Field="TemperatureF" Title="Temp. F" />
        <GridColumn Field="Summary" />
    </GridColumns>
</TelerikGrid>

@code {

    //List<WeatherForecast> forecasts { get; set; } = new List<WeatherForecast>(); // Works fine!


    List<WeatherForecast> forecasts { get; set; } //Need to sort a field to show the rows

    protected override async Task OnInitializedAsync()
    {
        //forecasts = new List<WeatherForecast>(); //this helps

        forecasts = await Http.GetJsonAsync<List<WeatherForecast>>("WeatherForecast");

        //these do not help
        //await Task.Delay(200);
        //StateHasChanged();
    }
}