Ireland virtually wrapped up their last practice game when they dismissed Canada for a paltry 115 in less than 33 overs, with Langford-Smith (4-41) doing the maximum damage.
The Canadian total was too small to put pressure on Ireland, who scored 116-3 to emerge winners with more than 23 overs to spare.
"We bowled in good areas and were rewarded. It was good to be in a position like we were after bowling," said Irish skipper Trent Johnston.
"Langford-Smith worked very hard after a tournament in Kenya. He is running in well, bowling well and his confidence is sky-high after getting seven or eight wickets in the first two games."
Irish opener Jeremy Bray was the match's top scorer with 41, while Andre Botha contributed an unbeaten 22.
The Canadian batsmen earlier faltered against Langford-Smith, with opener Geoff Barnett (27), Qaiser Ali (17) and Ashif Mulla (11) only reaching double-figures.
"It sure is a big disappointment. They bowled in good areas and never allowed us to play shots. I think our preparations, minus today's outing, for the World Cup are pretty well," said Canadian captain John Davison.
Langford-Smith, who took three wickets against South Africa in the opening practice game, was well-supported by Kyle McCallan who grabbed two scalps for no run.
Ireland, who tested top-ranked South Africa before losing by 35 runs, are in Group D with Pakistan, the West Indies and Zimbabwe. Canada are in Group C with England, New Zealand and Kenya.
The top two sides from each group with qualify for the Super Eight stage.
Canada 115 in 32.5 overs (Geoff Barnett 27, Qaiser Ali 17, Ashif Mulla 11; Dave Langford-Smith 4 for 41, Kyle McCallan 2 for 0) lost to Ireland 116 for 3 in 26.5 overs (Jeremy Bray 41, Andre Botha 22 n o) by seven wickets.