>I have a customer record, which has one or more account records. Each account can have one or more invoice headers, each with one or more invoice detail records. I wrote a class for each.
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>When I create an instance of a customer class and call LoadCustomer, should that process also create a collection of accounts on the customer class. Then, should each account create a collection of invoice headers, which in turn would create a collection of invoice details?

I'm assuming you're talking about DataSets? This is the area where DataSets got a little fuzzy for me (I admit it's probably from my own lack of knowledge) and it why I switched to custom objects.