WPF revealed files through the shell COM API (SHOpenFolderAndSelectItems):
selecting several assemblies and choosing "Open Containing Folder" opened
one Explorer window per folder with all of that folder's files selected,
reusing a window already open at the location. The Avalonia port replaced
this with explorer.exe /select, invoked once per file, so revealing N
assemblies spawned N new windows and a single reveal never reused an
existing one.
Restore the shell-COM reveal on Windows behind the existing cross-platform
ShellHelper, grouping the selection by containing folder. macOS keeps a
single Finder "open -R" for the whole selection; Linux, lacking a portable
select-item hook, opens each distinct parent folder once instead of one
window per file. The folder grouping is a pure, unit-tested seam so the
behaviour is verified without launching the OS file manager.
The Windows COM portion is adapted from the pre-Avalonia ShellHelper; its
author's copyright notice is retained per its MIT license.
Assisted-by: Claude:claude-opus-4-8:Claude Code
Siegfried Pammer
7d975ef845