DataGrid with Fluent theme does not update when changing theme mode

[SamVanheer]

Describe the bug
When using a DataGrid in an application that uses Fluent theme, changing the theme mode from light to dark or vice versa does not update the grid theme.

To Reproduce
Steps to reproduce the behavior:

1. Create an application that uses Fluent theme and DataGrid
2. Add a datagrid to the main window
3. Add button or other input method to change the fluent theme mode
4. Grid header does not change

Expected behavior
The datagrid should change themes just like built-in controls.

Screenshots

Desktop (please complete the following information):

• OS: Windows 10
• Version 0.10.18

Additional context

Restarting the application and having the theme applied from the start works as expected.

I included the DataGrid fluent theme in my App.axaml:

<Application.Styles>
    <FluentTheme Mode="Light"/>
    <StyleInclude Source="avares://Avalonia.Controls.DataGrid/Themes/Fluent.xaml"/>
</Application.Styles>

The DataGrid control does not use custom styles or templates.

I'm changing the theme like this:

if (Application.Current!.Styles[0] is FluentTheme theme)
{
    theme.Mode = FluentThemeMode.Light; //FluentThemeMode.Dark;
}

[maxkatz6]

See #7659

Also it was fixed in 11.0 I think https://github.com/AvaloniaUI/Avalonia/pull/8163/files

[SamVanheer]

Thanks, 11.0.0-preview3 works properly.

[Sputnik24]

Cannot confirm. With 11.0.0-preview5, workaround is still needed. Without, it looks like this:

[timunie]

@Sputnik24 I don't think it's the same issue. The appereance is similar, however now even the white background is there if you start with dark theme applied. If no issue for this is open, please open a new one.

[maxkatz6]

Not the same issue, but observable problem and workaround are the same.

[0x90d]

I can confirm that it was working fine without workaround in preview 4 (I havent used any earlier preview versions). In preview 5 its broken (again?).

[0x90d]

I cannot get the "workaround" to work. But there is also no code snippet, maybe I'm doing something wrong. What's more weird is that if I remove Datagrid style from App.xaml and add it in code after changing to dark mode, the Datagrid Column Headers are still white:

Before I've tried (the order of removing and adding seems to be unrelated. I tried removing / adding before and after changing to dark without any difference):

Can someone please post the mentioned workaround or tell me what I'm doing wrong?