Unplanned
Last Updated: 08 Jan 2026 07:45 by ADMIN
Created by: Sascha
Comments: 5
Category: UI for Blazor
Type: Bug Report
10

In our application we use some large datasets and present them in a TelerikGrid. We use WPF + Blazor Hybrid and noticed, that in some cases the memory usage of the Web View process grows up to some gigabytes.

Here a screenshot of the task manager with a lot of RAM usage for the web view.

Here a screenshot of the detached DOM elements after a two navigations. The container divs are not garbage collected.

I tracked down the issue to come from the TelerikGrid, because when I remove it from the pages, everything runs fine. I also removed all GridColumns and the issue is still present. In the developer tools I noticed that one of the parent div elements remains in memory every time I navigate back and forth.

I also created a blank Blazor WebAssembly Standalone application and added a simple instance of the grid. Here, the issue is also present. I attach the one blazor page that causes the issue.

I've tested all major versions from 5.1 upwards, every version is affected.

Unplanned
Last Updated: 07 Jan 2026 14:02 by ADMIN
Created by: Isaac
Comments: 3
Category: UI for Blazor
Type: Feature Request
1

Magnifiable Image Component

A Blazor component designed to provide an interactive image magnification experience, similar to popular eCommerce websites.

Features

  • Interactive Magnifier: On mouse hover, a magnifier appears beside the image, following the cursor and displaying a zoomed-in portion of the image. At the same time an overlay appears on the image indicating the zoomed-in portion of the image.
  • Screen Space Awareness: The magnifier dynamically stretches to fill the available space to the right or left of the image, ensuring optimal use of the viewport and consistent margins.
  • Popover Integration: Utilizes Telerik's Popover for the magnifier, ensuring it appears above all other UI elements and avoids clipping or stacking issues.
  • Configurable Magnification: The magnification scale is configurable via the MagnifyScale parameter.
  • Accessibility: The image is wrapped in a button for keyboard accessibility, and all images support alt text.
  • Full-Size View: Clicking the image opens a modal window displaying the image at its actual size.

Sample Code

MagnifiableImage.razor

@inject IJSRuntime JS
@using Microsoft.JSInterop

@* Container *@
<div @ref="_containerRef" class="@($"magnifiable-image-container {Class}")" style="height: @Height;  width: @Width;">
    
    @* Image *@
    <button @onclick="@OnClick" class="magnifiable-image-button">
        <img src="@Image.Src" alt="@Image.Alt" style="height: 100%; width: 100%;"
             @onmousemove="@OnMouseMove" @onmouseenter="@OnMouseEnterAsync" @onmouseleave="@OnMouseLeave"/>
    </button>
    
    @* Magnifier *@
    <TelerikPopover @ref="_popoverRef" AnchorSelector=".magnifiable-image-container" Position="@(_showOnRight ? PopoverPosition.Right : PopoverPosition.Left)" Offset="@MagnifierMargin"
                    Width="@($"{_magnifierWidth}px")" Height="@($"{_magnifierHeight}px")" Class="popover-magnifier" Collision="PopoverCollision.Fit">
        <PopoverContent>
            
            @* Magnified Image *@
            <img src="@Image.Src" alt="@Image.Alt" class="magnified-image"
                 style="@($"width: {_magnifiedImageWidth}px; height: {_magnifiedImageHeight}px; transform: translateX({_magnifiedImageTransformX}px) translateY({_magnifiedImageTransformY}px); left: {_magnifiedImageLeft}px; top: {_magnifiedImageTop}px;")"/>
        
        </PopoverContent>
    </TelerikPopover>
    
    @* Magnifier Overlay *@
    @if (_isMouseOver)
    {
        <div class="magnifier-overlay" 
             style="@($"width: {_magnifierOverlayWidth}px; height: {_magnifierOverlayHeight}px; transform: translateX({_magnifierOverlayTransformX}px) translateY({_magnifierOverlayTransformY}px);  left: {_magnifierOverlayLeft}px; top: {_magnifierOverlayTop}px;")))">
        </div>
    }
    
    @* Actual Image *@
    <TelerikWindow @bind-Visible="@_isClicked" Modal="true" CloseOnOverlayClick="true" Draggable="false" Resizable="false" Class="window-rounded">
        <WindowActions>
            <WindowAction Name="Close"/>
        </WindowActions>
        <WindowContent>
            <img src="@Image.Src" alt="@Image.Alt"/>
        </WindowContent>
    </TelerikWindow>
    
</div>

<style>
    .magnifiable-image-container {
        position: relative;
        display: inline-block;
        cursor: zoom-in;
    }
    
    .magnifiable-image-button {
        background: none;
        border: none;
        padding: 0;
        margin: 0;
        font: inherit;
        color: inherit;
        cursor: inherit !important;
        outline: none;
        box-shadow: none;
        appearance: none;
        -webkit-appearance: none;
        -moz-appearance: none;
        display: block;
        width: 100%;
        height: 100%;
    }
        .magnifiable-image-button:focus-visible {
            outline: none;
            box-shadow: 0 0 0 2px color-mix(in srgb, var(--kendo-color-on-app-surface, #424242) 50%, transparent);
        }
    
    .popover-magnifier {
        overflow: hidden;
        border-radius: 0;
        position: relative;
        top: @(_adjustForTelerikFit ? $"{(_showOnBottom ? "" : "-")}{MagnifierMargin/4}px" : $"{(_showOnBottom ? "" : "-")}{MagnifierMargin}px");
    }
    
    .magnified-image {
        position: absolute;
    }
    
    .magnifier-overlay {
        position: absolute;
        background: color-mix(in srgb, var(--kendo-color-primary, #1274AC) 15%, transparent);
        pointer-events: none;
        z-index: 5;
        box-sizing: border-box;
        display: block;
    }
</style>

@code 
{
    [Parameter] public required ImageInfo Image { get; set; }

    /// <summary>
    /// The height of the image (e.g., "200px", "100%", or "auto"). Default is "auto".
    /// </summary>
    [Parameter]
    public string Height { get; set; } = "auto";

    /// <summary>
    /// The width of the image (e.g., "200px", "100%", or "auto"). Default is "auto".
    /// </summary>
    [Parameter]
    public string Width { get; set; } = "auto";

    /// <summary>
    /// The magnification scale for the magnifier. Default is 3 (3x magnification).
    /// </summary>
    [Parameter] 
    public double MagnifyScale { get; set; } = 3;

    /// <summary>
    /// Applies additional CSS classes to the MagnifiableImage's root element for custom styling and visual modifications.
    /// </summary>
    [Parameter]
    public string Class { get; set; } = string.Empty;

    private const int MagnifierMargin = 24;
    
    // State for magnifier visibility and container reference
    private bool _isMouseOver;
    private bool _isClicked;
    private ElementReference _containerRef;
    private TelerikPopover? _popoverRef;

    // Image and magnified image dimensions
    private double _imageWidth;
    private double _imageHeight;
    private double _magnifiedImageWidth;
    private double _magnifiedImageHeight;
    
    // Magnifier position and size
    private bool _showOnRight = true;
    private bool _showOnBottom = true;
    private bool _adjustForTelerikFit;
    private double _magnifierWidth;
    private double _magnifierHeight;

    // Magnified image offset within the magnifier
    private double _magnifiedImageLeft;
    private double _magnifiedImageTop;
    
    // Mouse position clamping bounds
    private double _minMouseX;
    private double _minMouseY;
    private double _maxMouseX;
    private double _maxMouseY;
    
    // Mouse position and transform for magnified image
    private double _mouseX;
    private double _mouseY;
    private double _magnifiedImageTransformX;
    private double _magnifiedImageTransformY;

    // Magnifier overlay size and transform
    private double _magnifierOverlayWidth;
    private double _magnifierOverlayHeight;
    private double _magnifierOverlayLeft;
    private double _magnifierOverlayTop;
    private double _magnifierOverlayTransformX;
    private double _magnifierOverlayTransformY;

    private void OnClick()
    {
        _isClicked = true;
    }

    private async Task OnMouseEnterAsync()
    {
        _isMouseOver = true;
        _popoverRef?.Show();
        
        // Get layout info about the image container using getElementLayoutInfo from wwwroot/js/magnifiable-image.js
        var containerLayoutInfo = await JS.InvokeAsync<ElementLayoutInfo>("getElementLayoutInfo", _containerRef);
        
        // Store image size
        _imageWidth = containerLayoutInfo.Width;
        _imageHeight = containerLayoutInfo.Height;
        _magnifiedImageWidth = _imageWidth * MagnifyScale;
        _magnifiedImageHeight = _imageHeight * MagnifyScale;
        
        // Determine magnifier position based on available space
        _showOnRight = containerLayoutInfo.DistanceFromViewportRight >= containerLayoutInfo.DistanceFromViewportLeft;
        _adjustForTelerikFit = Math.Abs(containerLayoutInfo.DistanceFromViewportBottom - containerLayoutInfo.DistanceFromViewportTop) < 20;
        _showOnBottom = containerLayoutInfo.DistanceFromViewportBottom >= containerLayoutInfo.DistanceFromViewportTop;
        
        // Calculate magnifier size based on available space
        _magnifierWidth = _showOnRight 
            ? containerLayoutInfo.DistanceFromViewportRight - MagnifierMargin*2
            : containerLayoutInfo.DistanceFromViewportLeft - MagnifierMargin*2;
        _magnifierHeight = containerLayoutInfo.ViewportHeight - MagnifierMargin*2;
        
        // Center the magnified image in the magnifier
        _magnifiedImageLeft = (_magnifierWidth / 2) - (_imageWidth / 2); 
        _magnifiedImageTop = (_magnifierHeight / 2) - (_imageHeight / 2);
        
        // Calculate min and max mouse X/Y to prevent showing empty space in the magnifier
        _minMouseX = Math.Floor((_magnifierWidth / MagnifyScale) / 2);
        _minMouseY = Math.Floor((_magnifierHeight / MagnifyScale) / 2); 
        _maxMouseX = Math.Ceiling(_imageWidth - ((_magnifierWidth / MagnifyScale) / 2));
        _maxMouseY = Math.Ceiling(_imageHeight - ((_magnifierHeight / MagnifyScale) / 2));

        // Calculate magnifier overlay size and position
        _magnifierOverlayWidth = Math.Floor(Math.Clamp(_magnifierWidth / MagnifyScale, 0, _imageWidth)) - 1;
        _magnifierOverlayHeight = Math.Floor(Math.Clamp(_magnifierHeight / MagnifyScale, 0, _imageHeight)) - 1;
        _magnifierOverlayLeft = -((_magnifierOverlayWidth / 2) + 1);
        _magnifierOverlayTop = -((_magnifierOverlayHeight / 2) + 1);
    }

    private void OnMouseLeave()
    {
        _isMouseOver = false;
        _popoverRef?.Hide();
    }

    private void OnMouseMove(MouseEventArgs e)
    {
        // Clamp mouse X/Y to prevent showing empty space in the magnifier
        if (_minMouseX > _maxMouseX) _mouseX = _imageWidth / 2;
        else _mouseX = Math.Clamp(e.OffsetX, _minMouseX, _maxMouseX);
        if (_minMouseY > _maxMouseY) _mouseY = _imageHeight / 2;
        else _mouseY = Math.Clamp(e.OffsetY, _minMouseY, _maxMouseY);
        
        // Calculate the transform for the magnified image
        _magnifiedImageTransformX = -Math.Round((_mouseX * MagnifyScale) - (_imageWidth / 2));
        _magnifiedImageTransformY = -Math.Round((_mouseY * MagnifyScale) - (_imageHeight / 2));

        // Calculate the transform for the magnifier overlay
        _magnifierOverlayTransformX = Math.Round(_mouseX);
        _magnifierOverlayTransformY = Math.Round(_mouseY);
        
        _popoverRef?.Refresh();
    }

    private record ElementLayoutInfo(
        double Width, 
        double Height, 
        double ViewportHeight,
        double DistanceFromViewportLeft, // distance from viewport's left edge to element's left edge
        double DistanceFromViewportRight, // distance from element's right edge to viewport's right edge
        double DistanceFromViewportTop, // distance from viewport's top edge to element's top edge
        double DistanceFromViewportBottom); // distance from element's bottom edge to viewport's bottom edge
}

magnifiable-image.js

// Returns width, height, and the space to the left and right of the element relative to the viewport
window.getElementLayoutInfo = (element) => {
    if (!element) return null;
    const elementRect = element.getBoundingClientRect();
    return {
        width: elementRect.width,
        height: elementRect.height,
        viewportHeight: window.innerHeight,
        distanceFromViewportLeft: elementRect.left, // distance from viewport's left edge to element's left edge
        distanceFromViewportRight: window.innerWidth - elementRect.right, // distance from element's right edge to viewport's right edge
        distanceFromViewportTop: elementRect.top, // distance from viewport's top edge to element's top edge
        distanceFromViewportBottom: window.innerHeight - elementRect.bottom // distance from element's bottom edge to viewport's bottom edge
    };
};

Note

Only tested in Blazor WebAssembly. The component may see performance issues in Blazor Server.

Unplanned
Last Updated: 31 Dec 2025 10:54 by ADMIN
Created by: The Telerik
Comments: 0
Category: UI for Blazor
Type: Feature Request
0
Add Hourly Frequecy  option in In-bulit  Recurrence Frequecy Tabs
Unplanned
Last Updated: 30 Dec 2025 15:13 by Hélix

We use QueryableExtensions.ToDataSourceResultmethod to load some data in our component. And at some moment we need to cancel data loading. But ToDataSourceResult method doesn’t support CancellationToken. So we are forced to use a workaround and just ignore the task's result. But task is still executing and causing the performance hit

It would be great if you implemented support for this feature!

Unplanned
Last Updated: 26 Nov 2025 08:46 by Janick

Please expose the popup collision settings of the Popup and Popover components to all other applicable components, such as:

  • AutoComplete
  • ColorPicker
  • ComboBox
  • DropDownList
  • DatePicker
  • DateRangePicker
  • DateTimePicker
  • MultiColumnComboBox
  • MultiSelect
  • TimePicker
  • Tooltip
Unplanned
Last Updated: 14 Nov 2025 13:57 by ADMIN
Created by: Stefan
Comments: 0
Category: UI for Blazor
Type: Feature Request
1
Please add Blazor OTP input control
Unplanned
Last Updated: 13 Nov 2025 18:18 by Rob

I realize we can build Blazor components to associate "label" to controls, but IMHO, this should come standard with any control tool set. Reasons:

1.  Coding simplicity

2.  Automatic theme inheritance

3.  Flexibility in label positioning relative to the control (left, right, top, bottom)

Example:

<TelerikCheckBox Label="Is Chasssis" LabelPosition="left" @bind-Value="equipment.IsChassis"/>

 

I realize you folks put some effort into a "Floating Label", but my users have rejected this implementation because:

1.  Having Text in a label as a means to identify the label makes them think a value is already provided (so they try to remove it or call for support).

2.  When typing in the label and the appearance of the label identification appears above adds to their confusion as they are used to seeing validation errors appearing above a label.

 

 

 

Unplanned
Last Updated: 11 Nov 2025 11:03 by ADMIN
Created by: Kinga
Comments: 3
Category: UI for Blazor
Type: Feature Request
20

Hi,

is it possible to add control of vertical timeline like this (https://antblazor.com/en-US/components/timeline) with extra features like:

  • adding new items with button on top
  • inline edit
  • item selection
  • item actions

I also attached image of what i build based on control from link above, I would like to implement something similar with Telerik.

Maybe you can recommend some other controls to replace it with?

Thank you :)

Unplanned
Last Updated: 10 Nov 2025 10:33 by ADMIN
The IsEntityFrameworkProvider method in the DataSource package returns false when the provider is Entity Framework Core. 
Unplanned
Last Updated: 27 Oct 2025 11:21 by Deasun
Created by: Emil
Comments: 4
Category: UI for Blazor
Type: Feature Request
7
Is there a chance that there will be added a Treemap component in the near future?
Unplanned
Last Updated: 22 Oct 2025 07:54 by Ak
Make the demos possible to launch from a desktop shortcut, similarly to the UI for ASP.NET Core demos. 
Unplanned
Last Updated: 09 Oct 2025 09:48 by ADMIN
Created by: Olivier
Comments: 0
Category: UI for Blazor
Type: Feature Request
0

Hi !

I tried using the combobox but, since my datasource is too big and I need grouping, therefore virtualization is not possible, I need to do the filtering on the server side, using the OnRead method to fetch my data based on what the user has entered in the input field. The problem is that the client side filtering is always active and I can't reproduce the same type of filtering I do server side on the client side and I lose some results. I think it would be really nice if we could specify to not filter client side or something like that, to give us more control.

Thank you very much !

Unplanned
Last Updated: 06 Oct 2025 14:21 by Sadik

Description

Affected components: those inheriting from TelerikInputBase (e.g., TelerikDatePicker). When an exception is thrown inside an async Task event handler for the OnChange, OnBlur, OnOpen, and ValueChanged events, the exception is completely and silently swallowed. The exception is not caught by ErrorBoundary.

Related: #6333, #12364

Steps To Reproduce

  1. Use a standard ErrorBoundary in MainLayout.razor.
<ErrorBoundary>
    <ChildContent>
        @Body
    </ChildContent>
    <ErrorContent>
        <p class="error">An unhandled error has occurred.</p>
    </ErrorContent>
</ErrorBoundary>
  1. Declare a TelerikDatePicker and bind an async Task method to the ValueChanged or OnChange event.
<TelerikDatePicker Value="@DatePickerValue"
                   ValueChanged="@((DateTime inputDate) => OnDatePickerValueChanged(inputDate))">
</TelerikDatePicker>


<TelerikButton OnClick="@(() => throw new Exception("Exception from button"))">Click to test ErrorBoundary</TelerikButton>

@code {
    private DateTime DatePickerValue { get; set; } = DateTime.Today;

    private async Task OnDatePickerValueChanged(DateTime newValue)
    {
        throw new InvalidOperationException("This exception should be caught by the ErrorBoundary!");
    }
}
  1. Run the page and select a date in the DatePicker.

Actual Behavior

The exception thrown in the OnDatePickerValueChanged event handler is not caught by ErrorBoundary.

Expected Behavior

The exception thrown in the OnDatePickerValueChanged event handler is caught by ErrorBoundary.

Browser

All

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

No response

Unplanned
Last Updated: 06 Oct 2025 14:03 by Sadik

Description

Affected components: those inheriting from TelerikSelectBase (e.g., TelerikDropDownList, TelerikComboBox, TelerikMultiSelect, TelerikAutoComplete). When an exception is thrown inside an async Task event handler for the OnChange, OnBlur, OnOpen, and ValueChanged events, the exception is completely and silently swallowed. The exception is not caught by ErrorBoundary.

Related: #6333

Steps To Reproduce

Steps to Reproduce

  1. Use a standard ErrorBoundary in MainLayout.razor.
<ErrorBoundary>
    <ChildContent>
        @Body
    </ChildContent>
    <ErrorContent>
        <p class="error">An unhandled error has occurred.</p>
    </ErrorContent>
</ErrorBoundary>
  1. Declare a TelerikDropDownList and bind an async Task method to the ValueChanged or OnChange event.
<TelerikDropDownList 
    Data="@DropDownData"                  
    ValueChanged="@( (int newValue) => OnDropDownValueChanged(newValue))"       
    TextField="@nameof(TestItem.Name)"
    ValueField="@nameof(TestItem.Id)" />

<TelerikButton OnClick="@(() => throw new Exception("Exception from button"))">Click to test ErrorBoundary</TelerikButton>

@code {
    private int? SelectedDropDownValue;

    private List<TestItem> DropDownData = new()
    {
        new() { Id = 1, Name = "Select me to throw exception" },
    };

    private async Task OnDropDownValueChanged(int newValue)
    {
        throw new InvalidOperationException("This exception should be caught by the ErrorBoundary!");
    }

    public class TestItem
    {
        public int Id { get; set; }
        public string Name { get; set; } = string.Empty;
    }
}
  1. Run the page and select the item in the DropDownList's list.

Actual Behavior

The exception thrown in the OnDropDownValueChanged event handler is not caught by ErrorBoundary.

Expected Behavior

The exception thrown in the OnDropDownValueChanged event handler is caught by ErrorBoundary.

Browser

All

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

No response

Unplanned
Last Updated: 26 Sep 2025 08:08 by ADMIN
Created by: improwise
Comments: 9
Category: UI for Blazor
Type: Feature Request
58

I'd like to have an ExpansionPanel component where I can declare my desired panel instances and their content in the markup.

Similar to https://www.telerik.com/kendo-angular-ui/components/layout/expansionpanel/

Unplanned
Last Updated: 25 Sep 2025 11:45 by ADMIN
Created by: Maria
Comments: 6
Category: UI for Blazor
Type: Feature Request
78

I would like a comopnent similar to this one https://demos.telerik.com/kendo-ui/dropdowntree/index

The goal is to be able to show and select hierarchical data, because the multiselect is flat https://demos.telerik.com/blazor-ui/multiselect/overview

Unplanned
Last Updated: 19 Sep 2025 09:46 by Thomas

One really nice feature MudBlazor UI has is the Dialog component. You can pass a component to the Dialog Service and it will display it in a modal dialog.

Existing Example

An example of this would be:

             var orderParams = new DialogParameters();
                orderParams.Add("SelectedOrderHeader", Item);
                orderParams.Add("EditMode", "Add");
                orderParams.Add("SelectedOrderDetail", new OMSOrderDetail());
          
                DialogService.Show<OrdersDetailForm>("Click on orders grid to continue", orderParams);

 

<OrderDetailsForm> is a custom Blazor component.

Does the Telerik Blazor dev team have any plans for implementing something like this?

          
Unplanned
Last Updated: 18 Sep 2025 08:34 by ADMIN
Created by: Thomas
Comments: 1
Category: UI for Blazor
Type: Feature Request
2

Hello,

I would like to have the Polar chart available in Blazor.

Radar Chart are nice but the categorical axis are not usable when having directional data to display

Thank you

Thomas


Unplanned
Last Updated: 21 Aug 2025 15:16 by ADMIN
Created by: Margaret
Comments: 1
Category: UI for Blazor
Type: Feature Request
0
I would like to have the ability to automatically resize the month view calendar row height to fit the amount of events. For example, if a user only has 1 event a day, I'd like the calendar row height to be short / compact to fit only the necessary space for that 1 event. If the user has 20 events, I'd like the row to resize so all of them fit without hiding any (see ticket Ticket 1695856). Thank you. 
Unplanned
Last Updated: 14 Aug 2025 06:01 by ADMIN

I have a grid with inline-edit mode where the items have data annotations validation enabled.
When I click the grid command button "add", and then without typing in anything submit in some way, the validation jumps in as it should.

However, if I - without providing more input and still in the same item's edit mode - just click the "add" button again and then submit the item again, the incomplete item is submitted without any further validation.

This is fatal for my purpose, and I can even reproduce the issue here on the Telerik website's example repl: Blazor Grid Editing Inline Editing - Telerik UI for Blazor (after turning off the option "Confirm Cancel Commands").

I would very much appreciate any guidance on how to circumvent that bug while it ist being worked on, since I couldn't yet find a way how to do it.
(As implied above, the confirmation prompt does prevent the bug, however I don't want to use a prompt if possible.)

Here's a list with some cases concerning this bug:
- tap add, submit => validation
- tap add, tap add, submit => submitted!
- tap add, submit (=> validation), tap add, submit => submitted!

Greetings to the team!

1 2 3 4 5 6