Last Updated: 01 Dec 2023 14:07 by ADMIN
Release 5.1.0 (31 Jan 2024) (R1 2024)
Created by: Peter
Comments: 1
Category: UI for Blazor
Type: Bug Report

So, brand new machine (Win 11 pro 64bit), brand new install of Visual Studio & Telerik, use the Telerik templates to create a new Blazor Server project.

When I run the application (with changes or first run), it takes almost a minute to start the application.

Without changes it starts in 2 seconds.

The fix is to add the following to the application's csproj file.


After the fix, it takes an just a little longer to run than without changes.  Since I have not heard back on my support ticket, I wanted to report this as a bug so hopefully it can get upvoted and we can get an answer to this issue. 

Original support ticket 

My Setup:

7950x, 32 gb DDR5 ram, WD Black SSD 850x SSD and slower internet 150mbit/s

Similar problem with my new laptop which is about 50% slower but exactly the same issue.



Last Updated: 01 Dec 2023 14:04 by ADMIN
Scheduled for 5.1.0 (31 Jan 2024) (R1 2024)

Hi Telerik Support.

I am using TelerikComboBox with Virtualization and enabled Filtering.  If I filter for a text and then scroll down, the filter text gets cleared. I am using OnRead event to populate the combo box. But the same issue is seen with local data population in the below sample code.

I need to show the user the text they have entered even when they scroll down to the next page. Is there a solution for this? 



Last Updated: 01 Dec 2023 13:08 by Davy
Release 2.6.0
Created by: Milind
Comments: 6
Category: TextBox
Type: Bug Report



In the demo page of textbox if I type my name Milind (I have good typing speed), it doesn't show the complete word in textbox. Some of the chars are dropped.(Milind - Miind, Soham - soam, Shevade - Shvae) etc. Even the backspace key on keyboard doesnt seem to work properly. If I type the name at very slow speed I am able to retain all typed chars. It seems to be a bug

Attaching video for reference



Milind Shevade

Pending Review
Last Updated: 01 Dec 2023 07:36 by Amanullah
Created by: Amanullah
Comments: 0
Category: UI for Blazor
Type: Bug Report

I have a ComboBox that gets data from a remote service, using virtualization. When the PageSize property is big enough (in my case 20), I have issues scrolling down. I'm trying to scroll but it removes the input text.

You can use your own demo examples to replicate this issue. To reproduce the issue, try the ComboBox - Virtualization, in Telerik REPL (Demo)

Last Updated: 01 Dec 2023 06:56 by Miroslav

It seems that the issue appeared after upgrading to Telerik 5.0 from 4.6.

When using a Grid with a locked column and column virtualization enabled, focusing cell from that locked column breaks the layout on horizontal scrolling.

Last Updated: 30 Nov 2023 12:11 by Martin
Scheduled for 5.1.0 (31 Jan 2024) (R1 2024)

The issue is reproducible when the `AllowCustom` parameter is set to `true`.
Typing rapidly in the input field of the MultiColumnComboBox component causes the entered text to blink. Also, some of the inserted symbols are cleared.

Reproduction (if bug)

Open this demo:

Try to input text rapidly into the input field.

Last Updated: 29 Nov 2023 15:00 by ADMIN
Release 5.1.0 (31 Jan 2024) (R1 2024)
Created by: René
Comments: 0
Category: Tooltip
Type: Bug Report

Tooltip does not show if moving from one element with Tooltip to another and both elements are placed directly next to each other.

Example: If a number of Buttons (with title) are placed right next to each other if mouse is moved over the first one the tooltip is displayed correctly. If the mouse is moved to the next one the first tooltip closes but the second one does not show. Moving on to the third button the tooltip is displayed correctly again.

Last Updated: 28 Nov 2023 19:17 by ADMIN

Since upgrading from 3.8 to 4.4 (including all new css) created dialogs from DialogFactory are sometimes behind an already opened modal window.
The reason for this seems to be an incorrectly, automatically calculated z-index of 10003 when the open dialog has 10006.
This does not always happen, there are scenarios where the first created dialog works fine, and the next called in the same method suddenly is behind the dialog, thus the error seems to be in telerik and not our side.

We could not yet find a proper workaround apart from creating custom dialogs.

Last Updated: 27 Nov 2023 09:19 by Patrik Madliak

I've made a simple blazor repl demo here:

As you can see, TotalCount is 10, and the current PageSize is also 10. When these values match, the value in the "items per page" dropdown isn't present. Select any other value, and it will be present (for 5, 20, 40). Come back to 10, and again, the value disappears.

Last Updated: 27 Nov 2023 08:38 by ADMIN

If you use the pager whether in the grid, or on its own and the total number of rows in the underlying data source exactly matches the selected page size, the drop down will be displayed as blank.  This will only occur when there is no null "All" option in the list of page sizes.  By the looks of it, I would guess that there is code to select "All" whenever the total matches the selected page size option, but it selects nothing when the "All" option isn't in the list.  The functionality should select the page size that was selected by the user, not try to reset itself to All if the number of rows equals the page size.  The following repl shows the bug:

When you run the repl, change the page size to 5, and then back to 10.  You will see that the dropdown selects a blank item.  It should stay with 10.

Last Updated: 24 Nov 2023 06:29 by ADMIN
Scheduled for 5.1.0 (31 Jan 2024) (R1 2024)

The popup window is not closed when the ComboBox is disabled from code.

Reproduction code:


Selected value: @selectedValue
<br />

<TelerikComboBox Data="@myComboData"
                 ValueChanged="@((int value) => ValueChangedHandler(value))"
                 Placeholder="Select an item..."

@code {
    public bool isEnabled { get; set; } = true;
    IEnumerable<MyDdlModel> myComboData = 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

    public async Task ValueChangedHandler(int value)
        isEnabled = false;
        await Task.Delay(4000); //simulate network delay

        selectedValue = value;

        isEnabled = true;

    //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; }


Last Updated: 23 Nov 2023 21:53 by Marc
Created by: Srdjan
Comments: 9
Category: PDFViewer
Type: Bug Report
If you compare the print quality against the Kendo UI jQuery PDF viewer, the quality difference is night and day. We did not investigate what is happening under the hood in both components. However, the same printing dialog appears when printing via both components and both of them are web components, which indicates to us, that this issue is not related to the browser.
Last Updated: 23 Nov 2023 14:16 by ADMIN
Release 5.1.0 (31 Jan 2024) (R1 2024)
When using a Grid with a multi-column header which is locked, the layout breaks on horizontal scrolling. This behavior appears since Telerik UI Version 4.6 and also remains in 5.0.0 and 5.0.1.

See REPL sample (just use horizontal scroll):

When switching to Version 4.5 the Grid acts as expected.
Last Updated: 23 Nov 2023 13:17 by ADMIN
Release 5.1.0 (31 Jan 2024) (R1 2024)
I am using the Drag'N'Drop functionality of the Blazor TreeList and since the update to version 5.0.0 I cannot determine the destination component anymore, because the event argument parameter "DestinationComponentId" is always empty. I have assigned the ID of my TreeList components and everything worked well with version 4.6.0.

It does not matter whether I drag Items around within the same component or try to move them to another TreeList. The parameter is also empty when I try to drag items from a Grid to a TreeList.
Last Updated: 23 Nov 2023 08:55 by Mindaugas

TlerikDropDownList keyboard navigation works differently from native html select.

In case we have a list with many similar options, for example:
In this case with native html select I can type 02 to select 021, but with TlerikDropDownList this would select 211.

If you type swiftly multiple printable characters, the DropDownList keyboard navigation will react only to the first character.

Last Updated: 21 Nov 2023 20:05 by ADMIN
Created by: Haribabu
Comments: 3
Category: UI for Blazor
Type: Bug Report

Hi Support Team,

in our project we are using Telerik Chart and has required to update theme of chart from dark to light and light to dark.

telerik chart in child razor page and dark/light button in mainlayout.razor file but telerik chart updating theme when click on button exist telerik chart razor page. as below link  it is an existing issue.

please advice how to resolve the issue.

Last Updated: 21 Nov 2023 08:36 by Douglas

I have created a custom model where I added an ExpandoObject and a couple properties to it. The Grid seems to render the data successfully but the data operations are not possible - the nested properties are treated as invalid. Please add support for nested ExpandoObject properties in custom models.




For the time being, there is a workaround that you may try. Use the ExpandoObject directly, do not nest it in the custom model - bind the Grid Data to a collection of ExpandoObject and populate its properties in the OnInitialized.


@using System.Dynamic

<TelerikGrid Data="@Data" 
             Pageable="true" Sortable="true" Groupable="true"
             Resizable="true" Reorderable="true">
            <GridColumn Field="Id" FieldType="typeof(string)" Width="120px" />
            <GridColumn Field="DetailData.PropertyInt" Title="Column A" FieldType="@typeof(int)"  />
            <GridColumn Field="DetailData.ProptertyString" Title="Column B" FieldType="@typeof(string)"/>
            <GridColumn Field="DetailData.PropertyDate" Title="Column C" FieldType="@typeof(DateTime)"/>

@code {
    public ExpandoObject[] Data { get; set; } = Array.Empty<ExpandoObject>();

    protected override async Task OnInitializedAsync()
        Data = new ExpandoObject[]

    private ExpandoObject GetPopulatedExpando(int id)
        dynamic expando = new ExpandoObject();
        expando.Id = id;
        dynamic nested = new ExpandoObject();
        nested.PropertyInt = id;
        nested.ProptertyString = "ID " + id;
        nested.PropertyDate = new DateTime(2022, 4, id);
        expando.DetailData = nested;

        return expando;


Need More Info
Last Updated: 21 Nov 2023 06:38 by ADMIN
Created by: Kacper
Comments: 1
Category: UI for Blazor
Type: Bug Report


When I use TelerikDatePicker in my own component and the I use this component in Form, the validation for this input on the UI side doesn't work. The k-invalid class is not added, the appriopriate aria-invalid value is not set. The value on the TelerikDataPicker CascadedEditContext side is ok, an error message for this field appears after validation.

Last Updated: 20 Nov 2023 16:39 by ADMIN
Created by: Kacper
Comments: 3
Category: UI for Blazor
Type: Bug Report


This kind of behavior causes duplicate OnRead calls for the same range. If the OnRead method invokes a request to the API it will result in duplicate requests with the same range.


Last Updated: 20 Nov 2023 14:14 by Greg

My Nullable DateOnly field shows as 1/1/2001 - I would expect it to be a more sensible default. The problem is applicable only for the Form autogenerated DatePicker. The same issue is applicable for the TimeOnly type.



In the interim, as a viable workaround, you can utilize the FormItem Template and declare a TelerikDatePicker like this:

@using System.ComponentModel.DataAnnotations

<TelerikForm Model="@PersonModel">
                <label for="country">Date of Birth:</label>
                <TelerikDatePicker @bind-Value="@PersonModel.DOB" Width="200px" />

@code {
    private Person PersonModel { get; set; } = new Person() { DOB = null };

    public class Person
        [Display(Name = "Date of Birth")]
        public DateOnly? DOB { get; set; }


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