 Where a party transfers an asset to another in performance of a contract that is for some reason invalid, the shift of wealth is without good cause (or "sine causa"), and an enrichment action for the restitution of the asset lies.The other main types of quasi-contract are "negotiorum gestio" and "indebiti solutio".Many commercial transactions involve both the law of obligations and the law of property, and so have both proprietary and obligationary or contractual elements.