TabStrip v12.0.0

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Request a Feature Report a Bug

Completed

Last Updated: 15 Jan 2026 08:26 by ADMIN

Jamie

Created on: 13 Nov 2025 18:01

Category: UI for Blazor

Type: Bug Report

TabStrip v12.0.0

After upgrading to 12.0.0, the Content does not change when clicking tabs. I always see the Content of the first tab.

My project targets .net8.

6 comments

ADMIN

Dimo

Posted on: 15 Jan 2026 08:26

Hi Michal,

Using the TabStrip ActiveTabIndexChanged event without an ActiveTabIndex parameter is not a best practice or even valid. The same applies to any ParameterChanged event + Parameter combination in Blazor. So please set and update the parameter, according to the linked documentation example. Otherwise any UI refresh by the Blazor framework may reset the parameter value, because that value doesn't exist "officially" in the app.

The described scenario has worked by chance until version 12 due to how Blazor refreshed the TabStrip UI, which has now changed.

You can also migrate to ActiveTabId, because ActiveTabIndex is now deprecated and you should be getting compilation warnings about it.

Regards,
Dimo
Progress Telerik

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Michal

Posted on: 13 Jan 2026 12:24

Hello Dimo,

same here after upgrade. Here and there users cannot switch to another Tab. ActiveTabIndexChanged is called, but view doesnt switch to new "tab".

Before we were able to use TabStrip WITHOUT "ActiveTabIndex " in markup. Just with "ActiveTabIndexChanged=@SomeMethod "

at newer version there is breaking change:

you MUST use BOTH(So another "int actindex {get;set;}" property.),

or ONLY "ActiveTabIndex"

ADMIN

Dimo

Posted on: 17 Nov 2025 07:24

Hello Jamie,

ActiveTabIndex and ActiveTabIndexChanged are not deprecated yet, but will be in the future. We add such information in the release notes as a breaking change when the API is removed and no longer available. Before that we use at least one release cycle to mark the API as deprecated, which generates build warnings and developers have time to adjust the code.

On a side note, I didn't fully understand what your scenario and implementation are, so I can't comment if there is as bug in the TabStrip or not. I am closing the issue, but feel free to follow-up if you like.

Regards,
Dimo
Progress Telerik

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Jamie

Posted on: 14 Nov 2025 18:57

I see that TabIndex is deprecated. Switching to ActiveTabId has resolved the issue.

The release notes for v12 do not indicate breaking changes in TabStrip. Maybe this should be added?

Jamie

Posted on: 14 Nov 2025 14:12

The issue occurs when the ActiveTabIndexChanged event handler is used. I can reproduce the issue at blazorrepl.telerik.com

ADMIN

Dimo

Posted on: 14 Nov 2025 10:10

Hello Jamie,

Our TabStrip demos seem to be working as expected, so please provide more instructions on how to reproduce the problem.

If necessary, provide an isolated runnable example.

Regards,
Dimo
Progress Telerik

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