It was announced this week that the 24-year-old, who has scored 12 goals for the SPFL Championship side this season, has signed on at Dens Park next season.
"We're disappointed in the way Dundee have handled it," said Anderson. "The least they could have done was phone me or Donald Findlay and say 'we want to speak to your player'.
"We are very annoyed at the tactics Dundee have used. They should have left it until after the game at the weekend."