I'm not fluent in VB, but my best guess at the VB equivalent is:

Dim result = oParametersDataDictionaryField.OfType(Of Object())().OrderByDescending(Function(x) x[0])

Result should be an IEnumerable of Object arrays. You can add ToArray() or ToList() to the end if you want an array or list respectively.

As for using one of the generic collections over the VB collection, Microsoft does recommend that (http://msdn.microsoft.com/en-us/library/microsoft.visualbasic.collection.aspx, see the note under remarks). Both the VB collection and the generic List implement the IList and ICollection interfaces, so chances are most of what you are doing should be equivalent. Just create your List as List(Of Object()).