get all Vapp Templates in catalog

using the .net sdk...

How do you get all VappTemplates in a specific catalog?

I am able to successfully retrieve them all using vdc.GetVappTemplateRefs() but that doesn't let you specify or filter on a catalog.

is there a method to retrieve template refs by catalog or is there a way to filter the list i get using vdc.getVappTemplateRefs() ?

thanks in advance.