Completed
Last Updated: 09 Apr 2026 14:18 by ADMIN
Release 2025 Q3 (Aug)
Created by: Stefan
Comments: 3
Category: Upload
Type: Bug Report
8

Description

File data is not available in the Upload's OnSuccess event.

Regression in version 9.0.0 introduced with the addition of the chunk upload functionality.

https://github.com/telerik/blazor/blob/master/js/telerik-blazor/src/upload/upload.ts#L282-L288

Steps To Reproduce

  1. Attach a handler to the OnSuccess event:
<TelerikUpload SaveUrl="/api/upload/save"
               RemoveUrl="/api/upload/remove"
               OnSuccess="@OnSuccessHandler" />

@code {
    async Task OnSuccessHandler(UploadSuccessEventArgs e)
    {
        foreach (var file in e.Files)
        {
            Console.WriteLine($"Name = {file.Name}, Size = {file.Size}, Extension = {file.Extension}");
        }

        StateHasChanged();
    }
}
  1. Upload a file and try to access its Name, Size, and Extension properties in the event handler.

Actual Behavior

The properties have their default values (null for Name and Extension and 0 for Size).

Expected Behavior

The actual file data is accessible in the OnSuccess event handler.

Browser

All

Last working version of Telerik UI for Blazor (if regression)

8.1.1

Completed
Last Updated: 09 Apr 2026 12:45 by ADMIN
Release 2026 Q2

OnChange and OnBlur event for editors (TelerikTextBox, NumericTextBox, and others) is not fired in InCell edit mode with Tab key.

 

Completed
Last Updated: 09 Apr 2026 12:29 by ADMIN
Created by: Kjartan
Comments: 4
Category: Editor
Type: Feature Request
24
I would like to have support for @mentions in your editor, similar to GitHub, Facebook etc.
Completed
Last Updated: 09 Apr 2026 12:19 by ADMIN
Created by: Sérgio
Comments: 1
Category: Diagram
Type: Feature Request
0

Hello,

Currently the Telerik diagram component looks very promising but lacks the option to better control what's shown inside each DiagramShape (Block, node). Wouldn't it be possible to allow a Template renderfragment inside of these shapes so we can fully control what's shown? This way we can build more complex diagrams with images, text, buttons inside.

 

 

Completed
Last Updated: 09 Apr 2026 11:56 by ADMIN
Release 2026 Q2
Created by: Wolf-Günter
Comments: 2
Category: FileManager
Type: Bug Report
5
If the FileManager is nested inside an EditForm or a TelerikForm, it will trigger exceptions. Some of the nested components in the FileManager will require a ValueExpression, as if they are related to the form's EditContext.
Completed
Last Updated: 09 Apr 2026 08:35 by ADMIN
Release 2026 Q2
I am using a bool property to control whether the columns of the Grid would be virtualized. When I try to toggle the value of this property the feature is not enabled or disabled accordingly. 
Completed
Last Updated: 26 Mar 2026 12:49 by ADMIN
Release 2026 Q2

Set the PdfViewer document (data) value to null. As a result, an endless loader will appear.

===

ADMIN EDIT

===

A possible workaround for the time being is to re-initialize the component after clearing the file: https://blazorrepl.telerik.com/cHYwQola24zzBOAd02.

Completed
Last Updated: 26 Mar 2026 07:28 by ADMIN
Release 2026 Q2
Created by: Robert
Comments: 3
Category: Grid
Type: Bug Report
0
A virtual Grid does not handle well dynamic RowHeight changes. The virtual scrollbar is not refreshed and scrolling breaks.
Completed
Last Updated: 24 Mar 2026 14:04 by ADMIN
Release 2026 Q2
Created by: Ola
Comments: 0
Category: MultiColumnComboBox
Type: Bug Report
2
We are using the TelerikMultiColumnComboBox in AdaptiveMode.Auto and with an OnRead filter.

On small viewports and entering something in the searchbox, the key is cleared after entering just one char. This is only happening in the mobile view, otherwise it works fine and one can enter more characters.
Completed
Last Updated: 24 Mar 2026 14:03 by ADMIN
Release 2026 Q2

The Tooltip component throws a JavaScript error when the user opens an adaptive dropdown component and tries to interact with it:

Uncaught TypeError: popup.isParent is not a function

Here is a test page. Open the DropDownList on a narrow screen and click on the adaptive ActionSheet.

 

<TelerikButton Class="tooltip-target" Title="Telerik Tooltip">Button</TelerikButton>

<TelerikDropDownList Data="@ListItems"
                     @bind-Value="@SelectedValue"
                     TextField="@nameof(ListItem.Text)"
                     ValueField="@nameof(ListItem.Id)"
                     AdaptiveMode="@AdaptiveMode.Auto"
                     Width="300px" />
<TelerikTooltip TargetSelector=".tooltip-target"
                ShowOn="@TooltipShowEvent.Hover" />

@code {
    private List<ListItem> ListItems { get; set; } = new();

    private int SelectedValue { get; set; } = 3;

    protected override void OnInitialized()
    {
        ListItems = new List<ListItem>();
        for (int i = 1; i <= 5; i++)
        {
            ListItems.Add(new ListItem()
            {
                Id = i,
                Text = $"Item {i}",
                Category = $"Category {i % 6 + 1}"
            });
        }
        base.OnInitialized();
    }

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

 

Completed
Last Updated: 23 Mar 2026 21:38 by Lance
Release 6.1.0

In a filterable Grid, if a column is not bound to a field from the model the Grid uses, it throws with:

Error: System.ArgumentNullException: Value cannot be null. (Parameter 'nullableType')

Reproduction: https://blazorrepl.telerik.com/GyEUlFEs04AUJoJ601.

The issue is reproducible :

  • For `FilterRow` -  on initialization even if the column is not filterable.
  • For `FilterMenu` - on initialization when the column is filterable.

===

ADMIN EDIT

===

A possible workaround for the time being is to set the FieldType of the column: https://blazorrepl.telerik.com/wSugvFui10jhcpZy00.


Completed
Last Updated: 16 Mar 2026 14:02 by ADMIN
Release 2026 Q2
Created by: Michal
Comments: 3
Category: Filter
Type: Bug Report
0

Hello,

 at version 12.3.0 TelerikFilter is crashing "at load". Prior this version, same markup = ok.

Error: System.InvalidOperationException: Object of type 'Telerik.Blazor.Components.TelerikFilter' does not have a property matching the name 'ValueChanged'.

also in demo:

https://www.telerik.com/blazor-ui/documentation/components/filter/integration

usage:

<TelerikFilter @bind-Value="@AdvancedFilterValue">
	<FilterFields>
		@foreach (var it in GridDef.ColStore.Where(x => x.Verejny == true))
		{
			<FilterField Name="@it.FldName" Type="@it.FldType" Label="@it.VerejnyNazev"></FilterField>
		}
	</FilterFields>
</TelerikFilter>
Completed
Last Updated: 16 Mar 2026 14:00 by ADMIN
Release 2026 Q2

Currently, a TextField value of empty string will produce a blank item in the dropdown.

On the other hand, a null TextField value will produce the fully qualified class name.

Here are possible workarounds: https://blazorrepl.telerik.com/myOlFpFb1465jW8E07

Completed
Last Updated: 16 Mar 2026 06:37 by ADMIN
Release 2026 Q2
Created by: James
Comments: 0
Category: Grid
Type: Bug Report
0

An exception occurs if a Grid row is dropped in another empty Grid in RTL mode:

Error: System.FormatException: the input string '-1' was not in a correct format.

Completed
Last Updated: 13 Mar 2026 14:27 by ADMIN
Release 2026 Q2

There is an undocumented breaking change in the selection behavior of the v13.0.0 TreeView component that prevents us from upgrading from v12.3.0.

In v12.3.0, selecting a TreeView checkbox does change the TreeView item selection or trigger the selection change events. In v13.0.0, checking an item does also change the selection. The v12.3.0 behavior is important for our implementation because selecting a TreeView item in our application fetches data from a database and we do not want the performance overhead of those calls when checking an item---we want the user to be able to select multiple items and only then explicitly fetch the data for all of them.

I've created a minimal example here: https://blazorrepl.telerik.com/cqYdEePd40Zq3ava43. You can see the behavior differences when switching between versions.

Please let me know if there's any additional information we can provide. A workaround to this behavior would be appreciated. Thank you!

Completed
Last Updated: 13 Mar 2026 12:32 by ADMIN
Release 2026 Q2

I am using ComboBox and I want to be able to filter by two model properties. To achieve this I have implemented custom filtering through the OnRead event. Additionally, I am ordering the data to first match the results from the one property, which also is used for the TextField, and after that to match the results from the other property. However, when the results are only from the match of the second property, there is no focus.

Here is a REPL example https://blazorrepl.telerik.com/wyaMQhEN108axXJ036 

Steps to reproduce the issue:

Type "a": "Value test - ano" has the focus (the first option in the list)

Type "an": "Value test - ano" receives the focus (the first option in the list)

Type "ano": "Value test - ano" receives the focus (the first option in the list)

Type "anot": no item has focus despite the results being only "Another Value - val"

Completed
Last Updated: 12 Mar 2026 14:49 by Alex
Release 2026 Q2
If you focus an item, you can resize it with "Ctrl+Arrow keys". If you for example press "Ctrl+Arrow up", the items vertical size shrinks. If you do that repeatedly, it becomes less than 0. If you want to increase the size again, you first have to undo all that negativity, before the items grows again. Ideally, the code should only reduce "ColSpan" and "RowSpan" if its current value is greater than 1.
Completed
Last Updated: 12 Mar 2026 09:58 by ADMIN
Release 2026 Q2
The EventCallbacks "OnResize" and "OnReorder" only get invoked when a user is performing the appropriate actions with the mouse, not when using keyboard navigation.
Completed
Last Updated: 12 Mar 2026 09:58 by ADMIN
Release 2026 Q2
The parameters "Resizable" and "Reorderable" let you control whether tiles can be resized and reordered. These work when using the mouse, but once you turn on keyboard navigation via setting the parameter "Navigable" to "true", you are able to resize and reorder the tiles using "Ctrl"/"Shift" + "Arrow keys", regardless of the parameter values for "Resizable" and "Reorderable".
Completed
Last Updated: 12 Mar 2026 09:04 by ADMIN
Release 8.0.0

When a Dialog is shown from a modal Window, the Dialog appears behind the Window on second opening.

Here is a test page with a workaround:

@inject IJSRuntime js

<TelerikButton OnClick="@( () => WindowVisible = true )">Show Window</TelerikButton>

<TelerikWindow @bind-Visible="@WindowVisible"
               Modal="true">
    <WindowActions>
        <WindowAction Name="Minimize" />
        <WindowAction Name="Close" />
    </WindowActions>
    <WindowTitle>
        Window Title
    </WindowTitle>
    <WindowContent>
        <p>Window Content</p>
        <TelerikButton OnClick="@OnShowDialogButtonClick">Show Dialog</TelerikButton>
    </WindowContent>
</TelerikWindow>

<TelerikDialog @bind-Visible="@DialogVisible"
               Width="300px"
               Class="dialog-on-window">
    <DialogTitle>
        Dialog Title
    </DialogTitle>
    <DialogContent>
        <p>Dialog Content</p>
    </DialogContent>
    <DialogButtons>
        <TelerikButton OnClick="@( () => OnDialogButtonClick(true) )">OK</TelerikButton>
    </DialogButtons>
</TelerikDialog>

<script suppress-error="BL9992">
    function bringDialogToTop() {
        var dialogWrapper = document.querySelector(".dialog-on-window").closest(".k-dialog-wrapper");
        if (dialogWrapper) {
            dialogWrapper.style.zIndex = parseInt(dialogWrapper.style.zIndex) + 2;
        }
    }
</script>

@code {
    private bool WindowVisible { get; set; }

    private bool DialogVisible { get; set; }

    private bool ShouldFocusDialog { get; set; }

    private void OnShowDialogButtonClick()
    {
        DialogVisible = true;
        ShouldFocusDialog = true;
    }

    private void OnDialogButtonClick(bool result)
    {
        DialogVisible = false;
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        if (ShouldFocusDialog)
        {
            ShouldFocusDialog = false;
            await Task.Delay(1);

            await js.InvokeVoidAsync("bringDialogToTop");
        }

        await base.OnAfterRenderAsync(firstRender);
    }
}

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