We demonstrate crossbar all-optical switching (AOS) on an add-drop microring resonator on chip made of periodically poled lithium niobate. Utilizing quantum Zeno blockade (QZB) induced by sum-frequency generation, a signal is switched between the resonator's two output ports by a pump wave. The switching contrast is 3.35 and 8.27 dB, respectively, at the through and drop ports during a quasi-continuous operation and 5.15 and 9.01 dB during a pulsed operation. These results demonstrate a purely parametric approach to optical routing and computing for all-optical information processing.