Mapping class model to dto

Question

Trying to map a model class to service dto class where both have a custom class property.

i.e.

class Source { public CustomObject MyProperty {get;set;} }

class Destination { public CustomObject MyProperty {get;set;} }

However at the point of mapping, the Destination is Webservice.Destination, and so CustomObject is also Webservice.Destination. I'm unable to cast Source.MyProperty to Destination.MyProperty because it's casting from Model to Webservice. Is this even possible?