Grid
Column and row definitions can be specified in Avalonia using strings, avoiding the clunky syntax in WPF:
<Grid ColumnDefinitions="Auto,*,32" RowDefinitions="*,Auto">
A common use of Grid in WPF is to stack two controls on top of each other. For this purpose in Avalonia you can just use a Panel which is more lightweight than Grid.
Avalonia XPF - Cross-Platform WPF
Take your WPF apps to macOS and Linux in minutes, not months.