In this paper, consensus problems of continuous-time networked multi-agent systems via sampled control are investigated. The sampled control protocols are induced from continuous-time linear consensus protocol by using periodic sampling technology and zero-order hold circuit. Two cases are considered: 1) networks without sampling delay; 2) networks with sampling delay. For each case, an algebraic-type necessary and sufficient condition is obtained under which consensus is achieved. Some numerical simulations are presented, which are consistent with our theoretical results.