Net ionic equations are only formed during precipitant reactions which are when an aqueous cation and an aqueous anion react to form an insoluble solid. Since in your reaction the solid is in the reactants, and not the products, it is instead simply a double displacement reaction (not a precipitant) which doesn't dissociate like precipitants do.
If you did follow the similar process for creating the net ionic equation though you would get:
CdS(s) --> Cd⁺² + S⁻²
which obviously doesn't make sense (how can a solid react with itself to form ions?)
So, to answer your question, IMO there wouldn't be a net ionic equation (if I'm totally wrong though please call me on it lol).
Net ionic equations are formed when we have a reaction like:
BaCl₂(aq) + Na₂SO₄(aq) ---> BaSO₄(s) + 2NaCl(aq)
where the net ionic would be:
Ba⁺² + SO₄⁻² --> BaSO₄(s)
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