Checking for Values in SmartParts Before an Opportunity is Created in SalesLogix

Question: On the insert Opportunity form in SalesLogix I’m trying to check that
the products and contacts SmartParts contain values before a new
opportunity is created.  How can I refer to fields on a SmartPart within
a main form in SalesLogix?

Answer:  Instead of checking the values on the SmartParts, check the entity
property values.  If you would like to check if there is a product do
something like this:

Sage.Entity.Interfaces.