The problem at hand arises when attempting to update the CheckedItems property of a TreeView control from within an async method.

The problem seems to be timing-related and is not always reproducible. The issue is observed most often when starting the project. It seems to be reproducible only in Blazor Server App.

Reproduction:
To reproduce the issue, try running the following snippet in a Blazor Server App.

@page "/"
<TelerikTreeView Data="@FlatData"
                 CheckBoxMode="@TreeViewCheckBoxMode.Multiple"
                 CheckParents="@true"
                 CheckChildren="@true"
                 CheckOnClick="@false"
                 @bind-CheckedItems="@SelectedItems">
</TelerikTreeView>

@code {
    List<TreeItem> FlatData { get; set; }
    IEnumerable<object> SelectedItems { get; set; } = new List<object>();
    protected override async Task OnInitializedAsync()
    {
        await GenerateData();
        await SelectDefault();
    }

    async Task SelectDefault()
    {
        await Task.Delay(100);
        SelectedItems = FlatData.Where(data => data.Id == 2);
    }
#pragma warning disable
    async Task GenerateData()
    {
        FlatData = new List<TreeItem>();

        FlatData.Add(new TreeItem()
            {
                Id = 1,
                Text = "Project",
                ParentId = null,
                HasChildren = true,
                Icon = "folder",
                Expanded = true
            });

        FlatData.Add(new TreeItem()
            {
                Id = 2,
                Text = "Design",
                ParentId = 1,
                HasChildren = true,
                Icon = "brush",
                Expanded = true
            });
        FlatData.Add(new TreeItem()
            {
                Id = 3,
                Text = "Implementation",
                ParentId = 1,
                HasChildren = true,
                Icon = "folder",
                Expanded = true
            });
    }

    public class TreeItem
    {
        public int Id { get; set; }
        public string Text { get; set; }
        public int? ParentId { get; set; }
        public bool HasChildren { get; set; }
        public string Icon { get; set; }
        public bool Expanded { get; set; }
    }
}

The second TreeItem should be selected.

If the Height parameter is not specified, in the Gantt tree list, every line after the number of lines of the initial display are not shown.

The steps are easy to reproduce:

Start from the official Gantt Demo in the REPL and simply remove the Height parameter from TelerikGantt.

If you do this, you will see that opening the children of the first and only element in the tree list will show everything correctly in the Timeline part (if no mistake) but doesn't show the children lines in the TreeList part.

I have the following configuration:

Editor component in Grid EditorTemplate and the Grid editing mode is popup

Here is a REPL example https://blazorrepl.telerik.com/QeuUwsvb15sxbLuB04

The popup that opens when editing the Grid resizes when I type in the Editor

Steps to reproduce the issue:

1. Run the REPL example

2. Click the Edit button in the Grid

3. Resize the popup

4. Start to type something in the Editor

5. The popup resizes

I've determined that the TelerikDateTimePicker does not work properly on mobile devices when using AdaptiveMode.Auto. Attached are videos of the component's behaviour in both modes (None, and Auto).

Immediately after interacting with the fullscreen popup of the datepicker, I see this error in the console:

RAW:
telerik-blazor.js:50 Uncaught TypeError: r.isParent is not a function
    at p.isChild (telerik-blazor.js:50:1362352)
    at f.closePopup (telerik-blazor.js:50:1398427)
    at HTMLHtmlElement.onMouseDown (telerik-blazor.js:50:1397246)

Code:

@using Telerik.Blazor.Components
@using Telerik.Blazor

<TelerikFloatingLabel Text="Date & Time">
    <TelerikDateTimePicker Id="date-picker" @bind-Value="MyFormModel.Date" Max="@DateTime.Now.AddDays(1)"
                           Format="@DATE_FORMAT" AdaptiveMode="AdaptiveMode.Auto"
                           FillMode="@Telerik.Blazor.ThemeConstants.DateTimePicker.FillMode.Flat" />
</TelerikFloatingLabel>

@code {
    private FormModel MyFormModel { get; set; } = new FormModel();
    private const string DATE_FORMAT = "MM/dd/yyyy HH:mm";

    private class FormModel
    {
        public DateTime Date { get; set; }
    }
}

Notes:
- If we remove all of the parent components wrapping the DatePicker, it seems to function properly, but the errors remain in the console. This isn't a solution, however.

When Adaptive = true, changing the collection of buttons seems to "break" the adaptive calculation. The Toolbar fails to determine what are the buttons to show in the main element and what are the buttons to show in the pop-up: https://blazorrepl.telerik.com/wSubOWlS08FLz7aZ54

===

ADMIN EDIT

For the time being, a possible workaround is to force the component to refresh when you change the buttons. For that purpose, you can dispose it and re-initialize it after some delay. Here is a runnable sample: https://blazorrepl.telerik.com/QIOFuCvS400o5tfL34.

This is a continuation of public item DatePicker, TimePicker and DateTimePicker should accept null value as valid when bound to nullable DateTime

The problem persist when:

• The component Format includes a week day.
• The component Format is set with a standard date format string (d, D, g, etc.)

Test page with workarounds:

Bug due to week day format string inconsistency between .NET and JavaScript (dddd vs EEEE):

<TelerikDateTimePicker @bind-Value="@SelectedTime"
                       ShowClearButton="true"
                       Width="360px">
    <DateTimePickerFormatPlaceholder Weekday="week" />
</TelerikDateTimePicker>

<br />
<br />

Bug due to usage of a standard date format string:

<TelerikDatePicker @bind-Value="@SelectedTime"
                   ShowClearButton="true"
                   Format="d"
                   Width="360px">
    <DateTimePickerFormatPlaceholder Day="dd" Month="mm" Year="yyyy" />
</TelerikDatePicker>

@code {
    private DateTime? SelectedTime = DateTime.Now;
}

Hello,

after selecting a block of text in your editor and perform some block operation (for instance - change font size, name, ..) the original selection is lost. Would it be possible to keep that selection please?

Very thanks.

Miroslav

Hello, I would like to have a mutiselect dropdown like you have for ajax:

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

Syncfusion and radzen have this support for blazor :

https://blazor.syncfusion.com/demos/multiselect-dropdown/checkbox?theme=bootstrap5

https://blazor.radzen.com/dropdown

I know that you have a proposed solution for the MultiSelect component:

CheckBox in Multiselect

But the design of this one is not what I'm after, the box still expands downwards when selecting multiple items and it makes it hard to design a coherent page that does not make the dom "jump around". Also the implementation is cumbersome for more complex objects .

It would be better with a solution like you have for ajax where it just shows the first items that fits and then "+X items".

For some reason I'm unable to select the date 01/03/2000 when using the date picker to select the date. Only thing special about this date is its exactly 24 years ago today.

I was able to reproduce in repl. https://blazorrepl.telerik.com/QyYFkdbU34QbG0Te32

I also attached a video so you can review the steps followed and result.

The DateInput value disappears on focus when it is set with an async operation in OnInitializedAsync and AutoCorrectParts is false. Potentially related to Cannot select new DatePicker value from the Calendar when AutoCorrectParts is false

Test page with a workaround:

https://blazorrepl.telerik.com/cKkUaDbm09LYyPvg11

<p> The DateInput Value is: @DateValue </p>

@if (ShouldRenderDateInput)
{
    <TelerikDateInput @bind-Value="@DateValue"
                    Format="dd/MM/yyyy"
                    AutoCorrectParts="false"
                    Width="200px" />
}
@* the else block is optional to prevent delayed component appearance *@
else
{
    <TelerikDateInput @bind-Value="@DateValue"
                    Format="dd/MM/yyyy"
                    AutoCorrectParts="false"
                    Width="200px" />
}

@code {
    private DateTime? DateValue { get; set; }
    private bool ShouldRenderDateInput { get; set; }

    protected override async Task OnInitializedAsync()
    {
        await Task.Delay(200);
        DateValue = new DateTime(2026, 06, 22);
        ShouldRenderDateInput = true;
    }
}

When I click on the CheckBox's label, "Select All," the dropdown closes. While if I click the TelerikCheckBox itself, it remains open.

===

TELERIK EDIT

Possible workarounds include:

• Wrap the clickable UI in the MultiSelect HeaderTemplate in an element with a tabindex attribute: https://blazorrepl.telerik.com/mfOlnvFk40G8PElJ33
• Cancel the MultiSelect OnClose event conditionally: https://blazorrepl.telerik.com/QpYvxvla44M3nsdp57

Bug report

When a user navigates the DatePicker’s calendar using arrow keys, the component updates aria-activedescendant in the wrong order; it removes the id reference from the current cell before assigning it to the new cell. This creates a brief window in which aria-activedescendant points to an id that doesn't exist in the DOM.

Reproduction of the problem

(bug report only)
1. Run this example: https://blazorrepl.telerik.com/GgEKuoPQ289mGAyo13

Inspect the selected date in the calendar, select "break on attribute modification" for the td element of the selected date and the next td element. Navigate with "Right Arrow" key from the selected to the next date.

Current behavior

(optional)
The id of the selected date's td element is removed, but the DatePicker input’s aria-activedescendant attribute still has this id as value. Then the newly focused cell gets an id and it is set to the aria-activedescendant. 

Expected/desired behavior

The element referenced by aria-activedescendant must be in the DOM (https://www.w3.org/TR/wai-aria-1.2/#aria-activedescendant)

Environment

• Kendo/Telerik version: 14.0.0
• Browser: [all ]

At the moment start and end times effectively "round" to the nearest half an hour.   This can give the impression of events overlapping when they do not

e.g.

Admin edit: This feature would be similar to the Exact Time Rendering in our WebForms suite: https://demos.telerik.com/aspnet-ajax/scheduler/examples/exacttimerendering/defaultcs.aspx

The DateInput / TimePicker display the current Format instead of the component Value when the current culture / localization is not English (en).

DateTime values show as expected.