Got an example? :)

For example, App.xaml.cs:

Block-scoped namespace

namespace WinUIGallery
{
    /// <summary>
    /// Provides application-specific behavior to supplement the default Application class.
    /// </summary>
    sealed partial class App : Application
    {
        private static Window startupWindow;

File-scoped namespace

namespace WinUIGallery;

/// <summary>
/// Provides application-specific behavior to supplement the default Application class.
/// </summary>
sealed partial class App : Application
{
    private static Window startupWindow;

If you let Visual Studio create such a new file, what does it initially look like? Why would VS prefer one over the other?

Yeah. VS's item templates haven't been updated (yet?).
I'm bringing this up because, in the CommunityToolkit/Labs-Windows repo, I saw they are switching to file-scoped namespaces (CommunityToolkit/Labs-Windows#148), and I thought it might be a good idea to apply the same change here too. They also updated the editor.config to issue warnings for block-scoped namespaces.

Thanks for filing this issue. Would you want to take a stab at it?

Thanks for filing this issue. Would you want to take a stab at it?

@karkarl Of course!🙂