RadzenDropDownDataGrid: LoadData deadlock for async database-calls

[kuebelkasten]

I have this simple RadzenDropDown where the user can type a city-name and it will autocomplete what matches in the database.

  <RadzenDropDown AllowFiltering="true"                            
                        @* Count="_totalMatches" *@
                        Data="@_cities"
                        FilterDelay="300"
                        LoadData="HandleLoadDataAsync"
                        Placeholder="@(Localizer["Type the name of the city ..."])"
                        TValue="City"
                        ValueChanged="HandleValueChangedAsync">
    <Template>
        @((context as City)?.FormattedCityName)
    </Template>
</RadzenDropDown>

@code {
    [Parameter]
    public EventCallback<City> OnSelectedItemChange { get; set; }

    IEnumerable<City> _cities;

    private async Task HandleLoadDataAsync(LoadDataArgs loadData)
    {
       _cities = await DbContext.City.Where(...).OrderBy(...).Select(...).ToListAsync();

        await InvokeAsync(StateHasChanged);
    }

    private async Task HandleValueChangedAsync(TblCity city)
    {
        await OnSelectedItemChange.InvokeAsync(city);
    }
}

which all is working as expected. However, if I change to RadzenDropDownDataGrid and un-commenting (and setting) the Count-property I got a deadlock when HandleLoadDataAsync is invoked. I can see, that the SQL-is generated but it never goes further than the await ... ToListAsync() call.

First I thought this is an issue with the DbContext but I tried calling await DbContext...ToListAsync() in the OnInitializedAsync lifecycle-call which worked as expected. So I guess it has something to to with how the LoadData event-callback is invoked? Just guessing here as I wonder why it is working for RadzenDropDown but not for RadzenDropDownDataGrid.

Side note: Using the non-async calls will work but I still guess this is an issue/bug?

[enchev]

I'm unable to reproduce such exception. If you have Radzen subscription you can send us an repro application at info@radzen.com to debug it.

[Liam]

I ran into the same issue, was able to reproduce it by modifying the demo at:

radzen-blazor-master/RadzenBlazorDemos/Pages/DropDownDataGridPage.razor

Simply change the declaration of the LoadData() function to be async and add any async await to the first line:

    async Task LoadData(LoadDataArgs args)
    {
        await Task.Delay(100);

        var query = dbContext.Customers.AsQueryable();

When running the page, open the Custom filtering example dropdown and input any filter text, the filtering will not apply and elements on the page will stop responding.

[wjrm]

Any progress on this? I'm able to replicate it too.
I stumbled upon this when making an async call to db from LoadData.
Converting it to sync call works fine.

private void LoadData(LoadDataArgs args){
    var list = db.Table.ToList();
}

Converting it to async call makes the initial call, but fails when filtering, it deadlocks on ToListAsync.

private async Task LoadData(LoadDataArgs args){
    var list = await db.Table.ToListAsync();
}

Thank you

[SandroRiz]

Unfortunately I'm not able neither with the sync version...

The collection is filtered properly (I have a Count that changes when I type in the filter), but the grid remains always empty

Customers Count =  <span>@NavCustomers.ToList().Count()</span>
                                <RadzenDropDownDataGrid TValue="string" Data="@NavCustomers" TextProperty="FullName" ValueProperty="Id" @bind-Value="@(Complaint.ErpCustomerCode)"
                                                        FilterCaseSensitivity="FilterCaseSensitivity.CaseInsensitive" AllowFiltering="true" class="w-100" LoadData="@LoadCustomers"
                                                        AllowFilteringByAllStringColumns="true" FilterOperator="StringFilterOperator.Contains" AllowVirtualization="false">
                                   <Columns>
                                       <RadzenDropDownDataGridColumn Property="Id" Title="Id" Width="60px" />
                                        <RadzenDropDownDataGridColumn Property="CustomerName" Title="Nome" Width="240px" />
                                   </Columns>
                               </RadzenDropDownDataGrid>

public IEnumerable<NavCustomer> NavCustomers;

protected void LoadCustomers(LoadDataArgs args)
    {
        if (!string.IsNullOrEmpty(args.Filter))
        {
            NavCustomers =  NavCustomerService.Filter(args.Filter);
        }
        StateHasChanged();
    }

[SandroRiz]

I forgot the COUNT parameter that it seems it is mandatory even without virtualization.

BTW with 4.3.6 it works also with async methods

[enchev]

Count is mandatory for LoadData binding no matter if virtualization is on or off.