Need assistance with MultiValueProperty sorting methods

I need to sort an MVP before writing to AD.  Can anyone help me with the syntax for using the SortTopDown and SortBottomUp extension methods of MultiValueProperty?  I am not a .net programmer and am having difficulty understanding the documentation provided.

<ExtensionAttribute> _
Public Shared Function SortBottomUp(Of T, TKey) ( _
	input As IEnumerable(Of T), _
	keySelector As Func(Of T, TKey), _
	parentKeySelector As Func(Of T, TKey) _
) As IEnumerable(Of T)

What would I pass as the keyselector functions?

Dim mvpRoles As MultiValueProperty = New MultiValueProperty("a|d|c|b", "|")

Return mvpRoles.SortTopDown(???????)