<TelerikRootComponent>
    <TelerikGrid Data="@GridData"
                 Height="350px"
                 Sortable="true"
                 Pageable="true"
                 SortMode="@SortMode.Single"
                 FilterMode="@GridFilterMode.FilterMenu"
                 FilterMenuType="@FilterMenuType.CheckBoxList"
                 PageSize="10">
        <GridColumns>
            <GridColumn Field="Col1" Width="80px" Locked="true" />
            <GridColumn Field="Col2" Width="140px" />
        </GridColumns>
    </TelerikGrid>
</TelerikRootComponent>

@code { public List<dynamic> GridData = new List<dynamic>();

    protected async override Task OnInitializedAsync()
    {
        for (int i = 1; i < 10; i++)
        {
            dynamic row = new ExpandoObject();
            row.Col1 = $"col1_{i}";
            row.Col2 = $"col2_{i}";
            GridData.Add(row);
        }

    } }

<TelerikGrid @ref="@SafexTransactionGrid"
             Data=@SafexContractTransactionGridData
             ConfirmDelete="true"
             Pageable="true"
             Groupable="true"
             Sortable="true"
             FilterMode="GridFilterMode.FilterMenu"
             Resizable="true"
             Reorderable="true"
             EditMode="GridEditMode.Popup"
             SelectionMode="GridSelectionMode.Multiple"
             PageSize="15"
             Navigable="true">
    <GridColumns>
        ...
        <GridColumn Field="@nameof(SafexContractTransaction.Trader.Name)" Title="Trader Name" Editable="false"/>
        ...
    </GridColumns>
</TelerikGrid>

@code {

    private List<SafexContractTransaction> SafexContractTransactionGridData
    {
        get
        {
// returns all the data including populated Trader property
return FourtyTwoUnitOfWork.SafexContractTransactionRepo.GetAll(SafexContractGrid.SelectedItems);;
            }
        }
    }

    private TelerikGrid<SafexContractTransaction> SafexTransactionGrid { get; set; }

}
Yet when the grid is displayed it does not contain the property. 

How can I solve this? 

[13:07:52 ERR] Unhandled exception in circuit 'hQsJqY3F4XbTbzQETSggJClg_e4YRyQkrKHFMHCXugM'.
System.Threading.Tasks.TaskCanceledException: A task was canceled.
   at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, Object[] args)
   at Microsoft.JSInterop.JSRuntimeExtensions.InvokeVoidAsync(IJSRuntime jsRuntime, String identifier, Object[] args)
   at Telerik.Blazor.Components.TelerikComboBox`2.Dispose()
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__140_0(Object state)
   at Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext.ExecuteSynchronously(TaskCompletionSource`1 completion, SendOrPostCallback d, Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext.ExecuteBackground(WorkItem item)

<TelerikButton OnClick="@Change0">August</TelerikButton>
<TelerikButton OnClick="@Change">July</TelerikButton>
<TelerikButton OnClick="@Change2">June</TelerikButton>

@if (AllSales.Count > 0)
{
    <TelerikGrid @ref="@Grid" Data="@AllSales" Pageable="false">
        <GridColumns>
            <GridColumn Field="@nameof(MyViewModel.Product)">
            </GridColumn>
            <GridColumn>
                <HeaderTemplate>
                    <div>Sales by Date</div>
                </HeaderTemplate>
                <Columns>
                    @{
                        var dates = AllSales.First().SalesByDate.Keys.OrderByDescending(d => d).ToList();
                        foreach (var date in dates)
                        {
                            <GridColumn Title="@date.ToString("MM/dd")">
                                <HeaderTemplate>
                                    @{
                                        Console.WriteLine(date.ToString("MM/dd"));
                                        <div>@date.ToString("MM/dd")</div>
                                    }
                                </HeaderTemplate>
                                <Template>
                                    @{
                                        var record = context as MyViewModel;
                                        if (record.SalesByDate.ContainsKey(date))
                                        {
                                            <div>@record.SalesByDate[date]</div>
                                        }
                                    }
                                </Template>
                            </GridColumn>
                        }
                    }
                </Columns>
            </GridColumn>
        </GridColumns>
    </TelerikGrid>
}

@code {

    public class MyViewModel
    {
        public string Product { get; set; }
        public Dictionary<DateTime, decimal> SalesByDate { get; set; }
    }

    List<MyViewModel> AllSales { get; set; } = new List<MyViewModel>();
    TelerikGrid<MyViewModel> Grid { get; set; }

    protected override async Task OnInitializedAsync()
    {
        await base.OnInitializedAsync();

        Change0();
    }

    protected void Change0()
    {
        AllSales = new List<MyViewModel>();
        AllSales.Add(new MyViewModel
        {
            Product = "Product A",
            SalesByDate = new Dictionary<DateTime, decimal>
            {
                { new DateTime(2021,08,01), 1000 },
                { new DateTime(2021,08,02), 2000 },
                { new DateTime(2021,08,03), 3000 },
                { new DateTime(2021,08,04), 4000 },
                { new DateTime(2021,08,05), 5000 }
            }
        });
        AllSales.Add(new MyViewModel
        {
            Product = "Product B",
            SalesByDate = new Dictionary<DateTime, decimal>
            {
                { new DateTime(2021,08,01), 1000 },
                { new DateTime(2021,08,02), 2000 },
                { new DateTime(2021,08,03), 3000 },
                { new DateTime(2021,08,04), 4000 },
                { new DateTime(2021,08,05), 5000 }
            }
        });
    }

    protected void Change()
    {
        AllSales = new List<MyViewModel>();
        AllSales.Add(new MyViewModel
        {
            Product = "Product C",
            SalesByDate = new Dictionary<DateTime, decimal>
            {
                { new DateTime(2021,07,01), 1010 },
                { new DateTime(2021,07,02), 2020 },
                { new DateTime(2021,07,03), 3030 },
                { new DateTime(2021,07,04), 4040 },
                { new DateTime(2021,07,05), 5050 }
            }
        });
        AllSales.Add(new MyViewModel
        {
            Product = "Product D",
            SalesByDate = new Dictionary<DateTime, decimal>
            {
                { new DateTime(2021,07,01), 1010 },
                { new DateTime(2021,07,02), 2020 },
                { new DateTime(2021,07,03), 3030 },
                { new DateTime(2021,07,04), 4040 },
                { new DateTime(2021,07,05), 5050 }
            }
        });
    }

    protected void Change2()
    {
        AllSales = new List<MyViewModel>();
        AllSales.Add(new MyViewModel
        {
            Product = "Product E",
            SalesByDate = new Dictionary<DateTime, decimal>
            {
                { new DateTime(2021,06,01), 1100 },
                { new DateTime(2021,06,02), 2200 },
                { new DateTime(2021,06,03), 3300 }
            }
        });
        AllSales.Add(new MyViewModel
        {
            Product = "Product F",
            SalesByDate = new Dictionary<DateTime, decimal>
            {
                { new DateTime(2021,06,01), 1100 },
                { new DateTime(2021,06,02), 2200 },
                { new DateTime(2021,06,03), 3300 },
            }
        });
    }
}

<ColumnMenuTemplate>
<CustomColumnMenuItem/>
<ColumnMenuFiltering/>
<ColumnMenuSorting/>
....
</ColumnMenuTemplate>