<Border Background="#90707070" Visibility="{Binding Children.Sorting[SomePropertyName], Converter={StaticResource NullObjOrEmptyStrVisConverter}}" />
<Button FontFamily="Segoe MDL2 Assets"
Content="{Binding Children.Sorting[SomePropertyName], Converter={StaticResource SDToSymbolConverter}}" Command="{Binding Children.SortByPropertyCommand}" CommandParameter="SomePropertyName" />
</Grid>
</source>