Taxi scam in Hanoi

This is my first experiences when I travel in Hanoi. Actually, I know this scam is happening quite often in Thailand, Indonesia or Malaysia but maybe Vietnam is the worst.
The taxi driver tried to charge me more money from the airport to the city centre. The price is actually triple in comparison with locals. Although, it is not a big money for me but I feel very disappointed and uncomfortable. So I want to share this experiences with you guys. Beware to Vietnam, guys. It's full of scammers.