Clicking on the <label> opens the dropdown, but clicking on its main element does not

Selected value: @selectedValue
<br />
<label>some label for the dropdown, open it and test whether clicking outside closes it
    <TelerikDropDownList Data="@myDdlData" TextField="MyTextField" ValueField="MyValueField" @bind-Value="selectedValue">
    </TelerikDropDownList>
</label>

@code {
    //in a real case, the model is usually in a separate file
    //the model type and value field type must be provided to the dropdpownlist
    public class MyDdlModel
    {
        public int MyValueField { get; set; }
        public string MyTextField { get; set; }
    }

    IEnumerable<MyDdlModel> myDdlData = Enumerable.Range(1, 20).Select(x => new MyDdlModel { MyTextField = "item " + x, MyValueField = x });

    int selectedValue { get; set; } = 3; //usually the current value should come from the model data
}

When the Default text value is changed by some business logic, the component does not react to that change to update the Default text value in the view model.

DropDownList should re-render on change of the Default text parameter

DropdownList does not work very well with a screen reader.

It should work like this one https://www.w3.org/TR/wai-aria-practices-1.1/examples/listbox/listbox-collapsible.html

Using NVDA and Firefox, it reads the selected item 3 times, sometimes does not work at all (This is only when you open the dropdown using alt plus down arrow). Using just the arrow up and down keys does not work.

Using Cromevox and ChromeOn the dropdowns, it does not give a description of how many options are available like, "1 of 4" when you first tab to it. It reads it after I already selected the first option. That should be reversed, read the options first and not after its selected (This is only when you open the dropdown using alt plus down arrow). Using only the arrow key up and down it reads the selected item only but does not reads the other options.

The first element of the dropdown gets read aloud at page load even without being focused.

Using the latest version of (Chrome and Chromevox) and (Firefox and NVDA).

The DropDownList triggers exceptions if there are no items in the dropdown and one tries to use keyboard navigation:

• up/down arrows to change the selected item, no matter if the component is open or not
• Enter after filtering for non-existent item

Here is a test page. A possible workaround is to set DefautText, so that the dropdown always contains at least one  item.

Open and press Enter, Up or Down:

<TelerikDropDownList Data="@( new List<string>() )"
                     @bind-Value="@SelectedValue"
                     TItem="string"
                     TValue="string"
                     Width="200px" />

<br /><br />

Open, filter by something non-existent and press Enter, Up or Down:

<TelerikDropDownList Data="@DropDownData"
                     @bind-Value="@SelectedValue"
                     TItem="string"
                     TValue="string"
                     Filterable="true"
                     Width="200px" />

@code {
    string SelectedValue { get; set; }

    List<string> DropDownData = new List<string>()
    {
        "foo",
        "bar",
        "baz"
    };
}

When using the grouped DropDownList and performing a search for a specific element, the DropDownList incorrectly displays the initially shown group instead of the group containing the searched element.

Hi,

We are using the DropDownList component as an inline editor in the grid, for managing a product hierarchy. Previously we were using the DropDownList with grouping enabled, without virtualization, but due to volume of data we now need to use virtualization.
This does not work with grouping at the moment.

At the bottom of this page it is mentioned that 'Virtual scrolling with grouping will be supported in a future version.'.

Any timeline on this feature?

KR,

Lennert

The OnClose event fires multiple times when the handler uses the DialogFactory.

The behavior occurs with all select components (AutoComplete, ComboBox, DropDownList, MultiColumnComboBox, MultiSelect)

Possible workarounds include:

• Use a boolean flag to prevent the OnClose handler from executing the second time, for example, if the second execution occurs less than 1-2 seconds after the first one.
• Use OnChange instead of OnClose.
• Use a <TelerikDialog> component instead of ConfirmAsync.

Here is a test page that reproduces the issue:

<div style="display: flex; gap: 2em;">
    <div>
        <TelerikButtonGroup SelectionMode="@ButtonGroupSelectionMode.Single">
            <ButtonGroupToggleButton @bind-Selected="@UseOnChange">Use OnChange</ButtonGroupToggleButton>
            <ButtonGroupToggleButton @bind-Selected="@UseOnClose">Use OnClose</ButtonGroupToggleButton>
        </TelerikButtonGroup>

        <TelerikDropDownList Data="@Data"
                             @bind-Value="@Value"
                             ValueField="@nameof(SampleModel.Text)"
                             OnChange="@OnDropDownListChange"
                             OnClose="@OnDropDownListClose"
                             Width="160px" />

    </div>
    <div>
        <TelerikButton OnClick="@( () => CloseLog = string.Empty )">Clear Event Log</TelerikButton>
        <p>
            <pre>@CloseLog</pre>
        </p>
    </div>
</div>

@code {
    private List<SampleModel> Data { get; set; } = new();

    private string Value { get; set; } = string.Empty;
    private List<string> Values { get; set; } = new();

    private string CloseLog { get; set; } = string.Empty;

    private bool UseOnClose { get; set; } = true;
    private bool UseOnChange { get; set; }

    [CascadingParameter]
    public DialogFactory? TelerikDialogs { get; set; }

    private async Task OnDropDownListChange(object currentValue)
    {
        CloseLog += $"OnChange {DateTime.Now.ToString("HH:mm:ss.fff")} \n";

        if (UseOnChange)
        {
            await TelerikDialogs!.AlertAsync("OnChange");
        }
    }

    private async Task OnDropDownListClose(DropDownListCloseEventArgs args)
    {
        CloseLog += $"OnClose {DateTime.Now.ToString("HH:mm:ss.fff")} \n";

        if (UseOnClose)
        {
            await TelerikDialogs!.AlertAsync("OnClose");
        }
    }

    public class SampleModel
    {
        public int Id { get; set; }
        public string Text { get; set; } = string.Empty;
    }
}

When you select a date in DropDownList with dates in it (List<DateTime>), the @bind-Value is shaving off the milliseconds.

===ADMIN EDIT===

In the meantime, as a workaround for displaying milliseconds correctly, you can bind the DropDownList to a model. This way, you can use the "Id" to retrieve the selected item and display its precise milliseconds. Below is an example I've prepared to demonstrate this approach:

Selected value: @myDdlData.ToList().Where(x => x.Id == selectedValueId).FirstOrDefault()?.MyValueField.ToString("MM/dd/yyyy HH:mm:ss.fff")
<br />

<TelerikDropDownList Data="@myDdlData" 
                     TextField="MyTextField" 
                     ValueField="Id" 
                     @bind-Value="selectedValueId">
</TelerikDropDownList>

@code {
    public class MyDdlModel
    {
        public int Id { get; set; }
        public DateTime MyValueField { get; set; }
        public string MyTextField => MyValueField.ToString("MM/dd/yyyy HH:mm:ss.fff"); // Display formatted DateTime
    }

    private int selectedValueId { get; set; } = 1;

    private IEnumerable<MyDdlModel> myDdlData = GenerateRandomDateTimes(20);

    private static IEnumerable<MyDdlModel> GenerateRandomDateTimes(int count)
    {
        Random random = new Random();
        DateTime startDate = DateTime.Now;

        return Enumerable.Range(1, count)
            .Select(x => new MyDdlModel
            {
                Id = x, // Unique integer Id
                MyValueField = startDate.AddDays(x)
                    .AddMinutes(random.Next(0, 60))
                    .AddSeconds(random.Next(0, 60))
                    .AddMilliseconds(random.Next(0, 1000))
            }).ToList();
    }
}

The DropDownList is supposed to open the popup element when Alt-Down is pressed. This doesn't work if the page itself scrolls. Pressing alt-down scrolls the page instead. This is on macOS Safari and Chrome on a MacBook.

https://demos.telerik.com/blazor-ui/dropdownlist/keyboard-navigation

The problematic behavior can be reproduced in the following case:

• The DropDownList is at the lower part of the page, so the popup is rendered on top of the main element.
• The popup height is set to "auto".

In this scenario, when the user filters, the popup position remains unchanged but its height is reduced to fit the filter results. Thus, the popup looks detached from the main element. The behavior is not the same when the popup is rendered below the main element as in this case its top part sticks to the main element.

Reproduction: https://blazorrepl.telerik.com/mpEHGzOt25F1Znxi57.

===

ADMIN EDIT

===

When bound to a nullable GUID, the DropDownList invokes validation and shows validation messages as soon as the view loads.

Expected: the same behavior as with nullable int - validation is to be triggered by the form submission or selection from the dropdown.

Worked as expected in 1.2.0.

Reproducible:

Add the ability to make the drop down list expanded contents wider than the closed control, or just automatically determine appropriate width (doesn't always work well for very long text fields, so you need both properties).

See:  https://demos.telerik.com/aspnet-ajax/combobox/examples/functionality/dropdownconfigurator/defaultcs.aspx

Hello,

Initial I want no item to be selected to let the user select a value. I thought it would be enough if my bindvalue would be of a nullable type. I'm getting an exception when trying. If this is not supported, how can I do it?

     <div class="form-group col-md-2">
        <label class="col-form-label" for="ddReleaseType">Fönstertyp</label>
        <TelerikDropDownList Data="@ReleaseTypeFilterOptions" @bind-Value="FilterState.ReleaseType" TextField="DisplayText" ValueField="ReleaseType" Class="max-width form-control" @ref="ddReleaseType"></TelerikDropDownList>
    </div>

     public enum ReleaseType : int
    {
        All = 0,
        Category = 1,
        Season = 2,
        Misc = 3
    }

        protected Telerik.Blazor.Components.TelerikDropDownList<ReleaseTypeFilterModel?, SessionState.ReleaseType?> ddReleaseType;
 

        protected class ReleaseTypeFilterModel
        {
            public SessionState.ReleaseType ReleaseType { get; set; }
            public string DisplayText { get { return ReleaseType.ToString(); } }
        }
 

An unhandled exception occurred while processing the request.

Telerik.Blazor.Components.Common.TelerikSelectBase<TItem, TValue>.TryParseValueFromString(string value, out TValue result, out string validationErrorMessage)

• • Telerik.Blazor.Components.Common.TelerikSelectBase<TItem, TValue>.TryParseValueFromString(string value, out TValue result, out string validationErrorMessage)

  • Telerik.Blazor.Components.Common.TelerikSelectBase<TItem, TValue>.set_CurrentValueAsString(string value)

  • Telerik.Blazor.Components.TelerikDropDownListBase<TItem, TValue>.OnParametersSet()

  • Microsoft.AspNetCore.Components.ComponentBase.CallOnParametersSetAsync()

  • Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()

  • Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToPendingTasks(Task task)

  • Microsoft.AspNetCore.Components.Rendering.ComponentState.SetDirectParameters(ParameterView parameters)

  • Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InitializeNewComponentFrame(ref DiffContext diffContext, int frameIndex)

  • Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InitializeNewSubtree(ref DiffContext diffContext, int frameIndex)

  • Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.InsertNewFrame(ref DiffContext diffContext, int newFrameIndex)

  • Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.AppendDiffEntriesForRange(ref DiffContext diffContext, int oldStartIndex, int oldEndIndexExcl, int newStartIndex, int newEndIndexExcl)

  • Microsoft.AspNetCore.Components.RenderTree.RenderTreeDiffBuilder.ComputeDiff(Renderer renderer, RenderBatchBuilder batchBuilder, int componentId, ArrayRange<RenderTreeFrame> oldTree, ArrayRange<RenderTreeFrame> newTree)

  • Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment)

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.RenderInExistingBatch(RenderQueueEntry renderQueueEntry)

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()

  • Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue()

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessPendingRender()

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToRenderQueue(int componentId, RenderFragment renderFragment)

  • Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged()

  • Microsoft.AspNetCore.Components.ComponentBase.CallOnParametersSetAsync()

  • Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()

  • Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.HandleException(Exception exception)

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.AddToPendingTasks(Task task)

  • Microsoft.AspNetCore.Components.Rendering.ComponentState.SetDirectParameters(ParameterView parameters)

  • Microsoft.AspNetCore.Components.RenderTree.Renderer.RenderRootComponentAsync(int componentId, ParameterView initialParameters)

  • Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.CreateInitialRenderAsync(Type componentType, ParameterView initialParameters)

  • Microsoft.AspNetCore.Components.Rendering.HtmlRenderer.RenderComponentAsync(Type componentType, ParameterView initialParameters)

  • Microsoft.AspNetCore.Components.Rendering.RendererSynchronizationContext+<>c__11<TResult>+<<InvokeAsync>b__11_0>d.MoveNext()

  • Microsoft.AspNetCore.Mvc.ViewFeatures.StaticComponentRenderer.PrerenderComponentAsync(ParameterView parameters, HttpContext httpContext, Type componentType)

  • Microsoft.AspNetCore.Mvc.ViewFeatures.ComponentRenderer.PrerenderedServerComponentAsync(HttpContext context, ServerComponentInvocationSequence invocationId, Type type, ParameterView parametersCollection)

  • Microsoft.AspNetCore.Mvc.ViewFeatures.ComponentRenderer.RenderComponentAsync(ViewContext viewContext, Type componentType, RenderMode renderMode, object parameters)

  • Microsoft.AspNetCore.Mvc.TagHelpers.ComponentTagHelper.ProcessAsync(TagHelperContext context, TagHelperOutput output)

  • Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperRunner.<RunAsync>g__Awaited|0_0(Task task, TagHelperExecutionContext executionContext, int i, int count)

  • ReleaseCalendar.Pages.Pages__Host.<ExecuteAsync>b__14_1() in _Host.cshtml

    +
    18.     <app><component type="typeof(App)" render-mode="ServerPrerendered" /></app>

  • Microsoft.AspNetCore.Razor.Runtime.TagHelpers.TagHelperExecutionContext.SetOutputContentAsync()

  • ReleaseCalendar.Pages.Pages__Host.ExecuteAsync()

  • Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)

  • Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, bool invokeViewStarts)

  • Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)

  • Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, string contentType, Nullable<int> statusCode)

  • Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, string contentType, Nullable<int> statusCode)

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|29_0<TFilter, TFilterAsync>(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext<TFilter, TFilterAsync>(ref State next, ref Scope scope, ref object state, ref bool isCompleted)

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()

  • Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)

  • Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)

  • Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Hi!

When i use combination of LINQ inside TelerikDropDownLists Data attribute and TelerikGrid 's GridEditMode.Popup mode, i get weird behavior when i try to select an item from TelerikDropDownLists - everything freezes. Please check the solution. Everything works fine if i don't use LINQ or GridEditMode.Popup mode.

Thank you!

I have two cascaded dropdownlists, in attached example car brands and selectable colors. The dependent dropdown has defaulttext option. After the parent dropdown has changed, in its event handler I reload the dependent data source and set a new valid value. If the data source does not contain the previous (!) value, the dropdownlist calls the valuechanged callback with default value. In next round when dependent dropdown holds the default value, after reloading datasource it works as expected. And parent changes again, if the updated datasource does not contain the previous dependent value the dropdownlist sets its value to default.

When I do not pass defaulttext parameter, the dependent dropdown selects the first element from the updated datasource. In my case it is not acceptable because I want to set a specific value (in this example the default color), not the first and not the default.

This feedback drives me to try setting value to default and wait for re-render the descendant dropdownlist before set the wanted value. 

Is there any way to avoid this behaviour of the dropdownlist?

<TelerikDropDownList TItem="Brand"
			 TValue="int"
			 ValueField=@nameof(Brand.Id)
			 TextField=@nameof(Brand.Name)
			 Data="@BrandList"
			 Value="@Data.BrandId"
			 ValueChanged=@OnBrandChanged />

<TelerikDropDownList TItem="Color"
			 TValue="int"
			 ValueField=@nameof(Brand.Id)
			 TextField=@nameof(Brand.Name)
			 Data="@FilteredColorList"
			 Value="@Data.ColorId"
			 ValueChanged="@OnColorChanged"
			 DefaultText="select color ..." />

async Task OnBrandChanged(int brandId)
{
	Data.ColorId = default;
	await Task.Delay(5);
	Data.BrandId = brandId;
	Data.ColorId = GetDefaultColor(brandId);
	FilteredColorList = GetFilteredColorList(brandId);
}