In Mayor of City of N. Y. v. Manhattan Ry. Co. (143 NY 1) the Court held that a corporation, by performing a contract for the construction of subways, waived its right to defeat the City's claim for the payments due under the contract. The Court accepted the corporation's argument that the project had been authorized by a constitutionally defective statute but held that a constitutional mandate, enacted to serve a public purpose, nevertheless may affect only a private interest when the mandate is applied to a particular party (143 NY, at 26).