TabControl Tabs Don't Work After First Time Showing In DialogHost

[corvinsz]

Discussed in #4062

^{Originally posted by reillybainet June 3, 2026}
Using
VS 26
.NET 10-windows10.0.26100.0
MaterialDesignThemes 5.3.2

I have a simple main window that contains a DialogHost. When I click a button, I create a new StimulusDialog object which is a user control that is a grid containing the StimulusView contents and ok/cancel buttons. The StimulusView is just a tab control with 4 tabs. The ok/cancel buttons Command property is set to DialogHost.CloseDialogCommand.

The first time that I click the button in the main view, I can select the tabs and click ok or cancel.

After that, none of the tabs will select, but I can still ok or cancel.

I'm sure that I'm doing it wrong, but I can't figure it out. Here is a simple example that replicates my issue.

Any help is very appreciated!

Thanks.

-Reilly.

MdDialog.zip

[corvinsz]

I noticed when using the Style="{StaticResource MaterialDesignEmbeddedDialogHost}" for the DialogHost, the bug is no longer present. Not sure how this correlates to the TabControl yet though.

[nicolaihenriksen]

@corvinsz Nice catch with the embedded style! Looking at why there is a difference, I believe that is because the Popup, sets itself to IsHitTestVisible=False when the window is closing (see here).

In the OPs sample, I believe the actual StimulsView is being reused (i.e. same instance), and thus it will open up with PopupRoot.IsHitTestVisible=False on subsequent openings. It will probably be set to True shortly thereafter, but since we have already captured the False value, and reapply it when the initial animation ends, the TabControl never becomes hit test visible again. At least this is my working theory.

One option to consider could be to avoid the animation all together if TabControl.IsHitTestVisible == False when the TabControlHeaderScrollBehavior.AssociatedObject_ScrollChanged() callback fires. Thoughts?