Serializing an Object with a member of Type ArrayList

Question

Hello out there! I try to program a webservice which returns an object (lets call its class a) which contains an arrayList with several ohter objects of one common class (lets call it b). Running the programm i get told that the object of type b is not expected and that i shall use XmlInclude- or SoapInclude-Attributt for non-static-types. (Regarding xml-Include I have found some manual text that tells me what I can use the XmlIncludeAttribute for, but it was for serializing objects that inherit from the class that the method returns, so I don't see what I can use it for.) Can somebody give me some advice? Thanks in advance, rabbit