<TelerikGrid @ref="@GridInlineRef"
             Data="@GridInlineData"
             EditMode="@GridEditMode.Inline"
             OnAdd="@OnGridAddEdit"
             OnEdit="@OnGridAddEdit"
             OnCreate="@OnGridInlineCreate"
             OnUpdate="@OnGridInlineUpdate"
             OnRowClick="@OnGridRowClick">
    <GridToolBarTemplate>
        <GridCommandButton Command="Add">Add</GridCommandButton>
    </GridToolBarTemplate>
    <GridColumns>
        <GridColumn Field="@nameof(Product.Name)">
            <EditorTemplate>
                @{ var editItem = (Product)context; }
                <TelerikTextBox @ref="@NameTextBoxRef" @bind-Value="@editItem.Name" DebounceDelay="0" />
            </EditorTemplate>
        </GridColumn>
        <GridColumn Field="@nameof(Product.Price)">
            <EditorTemplate>
                @{ var editItem = (Product)context; }
                <TelerikNumericTextBox @ref="@PriceNumericTextBoxRef" @bind-Value="@editItem.Price" DebounceDelay="0" />
            </EditorTemplate>
        </GridColumn>
        <GridColumn Field="@nameof(Product.Stock)">
            <EditorTemplate>
                @{ var editItem = (Product)context; }
                <TelerikNumericTextBox @ref="@StockNumericTextBoxRef" @bind-Value="@editItem.Stock" DebounceDelay="0" />
            </EditorTemplate>
        </GridColumn>
        <GridCommandColumn>
            <GridCommandButton Command="Edit">Edit</GridCommandButton>
            <GridCommandButton Command="Save" ShowInEdit="true">Update</GridCommandButton>
            <GridCommandButton Command="Cancel" ShowInEdit="true">Cancel</GridCommandButton>
        </GridCommandColumn>
    </GridColumns>
</TelerikGrid>

@code {
    private TelerikGrid<Product>? GridInlineRef { get; set; }
    private TelerikTextBox? NameTextBoxRef { get; set; }
    private TelerikNumericTextBox<decimal?>? PriceNumericTextBoxRef { get; set; }
    private TelerikNumericTextBox<int>? StockNumericTextBoxRef { get; set; }
    private string EditFieldToFocus { get; set; } = string.Empty;

    private List<Product> GridInlineData { get; set; } = new List<Product>();

    private void OnGridAddEdit(GridCommandEventArgs args)
    {
        EditFieldToFocus = nameof(Product.Stock);
    }

    private async Task OnGridRowClick(GridRowClickEventArgs args)
    {
        EditFieldToFocus = args.Field;
        var itemToEdit = (Product)args.Item;

        args.ShouldRender = true;

        if (GridInlineRef != null)
        {
            var gridState = GridInlineRef.GetState();

            gridState.InsertedItem = null!;
            gridState.OriginalEditItem = itemToEdit;
            gridState.EditItem = itemToEdit.Clone();

            await GridInlineRef.SetStateAsync(gridState);
        }
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (!string.IsNullOrEmpty(EditFieldToFocus))
        {
            await Task.Delay(200);

            switch (EditFieldToFocus)
            {
                case nameof(Product.Name):
                    if (NameTextBoxRef != null)
                    {
                        await NameTextBoxRef.FocusAsync();
                    }
                    break;
                case nameof(Product.Price):
                    if (PriceNumericTextBoxRef != null)
                    {
                        await PriceNumericTextBoxRef.FocusAsync();
                    }
                    break;
                case nameof(Product.Stock):
                    if (StockNumericTextBoxRef != null)
                    {
                        await StockNumericTextBoxRef.FocusAsync();
                    }
                    break;
                default:
                    break;
            }

            EditFieldToFocus = string.Empty;
        }
    }

    #region Programmatic Inline Editing

    private async Task InlineAdd()
    {
        var gridState = GridInlineRef!.GetState();

        gridState.InsertedItem = new Product();
        gridState.InsertedItem.Name = "New value";
        gridState.OriginalEditItem = null!;
        gridState.EditItem = null!;

        await GridInlineRef.SetStateAsync(gridState);
    }

    private async Task InlineEdit()
    {
        if (GridInlineData.Any())
        {
            var gridState = GridInlineRef!.GetState();

            gridState.InsertedItem = null!;
            gridState.OriginalEditItem = GridInlineData.First();
            gridState.EditItem = GridInlineData.First().Clone();
            gridState.EditItem.Name = "Updated inline value";

            EditFieldToFocus = nameof(Product.Price);

            await GridInlineRef.SetStateAsync(gridState);
        }
    }

    private async Task InlineCancel()
    {
        var gridState = GridInlineRef!.GetState();

        gridState.InsertedItem = null!;
        gridState.OriginalEditItem = null!;
        gridState.EditItem = null!;

        await GridInlineRef.SetStateAsync(gridState);
    }

    private async Task InlineUpdate()
    {
        var gridState = GridInlineRef!.GetState();

        if (gridState.EditItem != null)
        {
            OnGridInlineUpdate(new GridCommandEventArgs()
            {
                Item = gridState.EditItem
            });
        }
        else if (gridState.InsertedItem != null)
        {
            OnGridInlineCreate(new GridCommandEventArgs()
            {
                Item = gridState.InsertedItem
            });
        }

        gridState.InsertedItem = null!;
        gridState.OriginalEditItem = null!;
        gridState.EditItem = null!;

        await GridInlineRef.SetStateAsync(gridState);
    }

    #endregion Programmatic Inline Editing

    #region Grid Inline Editing Handlers

    private void OnGridInlineUpdate(GridCommandEventArgs args)
    {
        var updatedItem = (Product)args.Item;
        var index = GridInlineData.FindIndex(i => i.Id == updatedItem.Id);
        if (index != -1)
        {
            GridInlineData[index] = updatedItem;
        }
    }

    private void OnGridInlineCreate(GridCommandEventArgs args)
    {
        var createdItem = (Product)args.Item;
        createdItem.Id = Guid.NewGuid();
        GridInlineData.Insert(0, createdItem);
    }

    #endregion Grid Inline Editing Handlers

    #region Data Generation and Model

    protected override void OnInitialized()
    {
        for (int i = 1; i <= 3; i++)
        {
            GridInlineData.Add(new Product()
            {
                Id = Guid.NewGuid(),
                Name = $"Product {i}",
                Price = Random.Shared.Next(1, 100) * 1.23m,
                Stock = (short)Random.Shared.Next(0, 1000)
            });
        }
    }

    public class Product
    {
        public Guid Id { get; set; }
        public string Name { get; set; } = string.Empty;
        public decimal? Price { get; set; }
        public int Stock { get; set; }
        public DateTime ReleaseDate { get; set; }
        public bool InProduction { get; set; }

        public Product Clone()
        {
            return new Product()
            {
                Id = Id,
                Name = Name,
                Price = Price,
                Stock = Stock,
                ReleaseDate = ReleaseDate,
                InProduction = InProduction
            };
        }
    }

    #endregion Data Generation and Model
}

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.