Wagner has played in the
Lakeside World Championship four times, reaching the last 16 on three occasions. In 2003, he beat
Gary Robson in the first round before going out after losing to
Erik Clarys. He beat
Co Stompé in the first round in 2004 before losing to
John Walton, and in 2005, he put out
Jarkko Komula in his first match, but lost to
Ted Hankey 3–2 in sets after leading 2–0. In 2008, Wagner reached the semi-finals of the Dutch Open where he lost to eventual winner
Robert Thornton, was runner up in the Finnish Open won by
Steve West, and won the Norway National Championship where he beat Rune David in the final. Wagner reached the semi-finals of the 2008 World Masters, beating
Gary Anderson in the last 16 and then beat
Joey ten Berge in the quarter-final before losing to
Scott Waites. Wagner played in the
2009 BDO World Championships, losing in the first round to Anderson. He then won the 2009 Finnish Open and retained the Norway National Championship. Wagner's best run in the World Championship came in 2010. He defeated
Alan Norris in the first round 3–1, to face
Brian Woods in the second round. Wagner came back from 2–0 and 3–2 behind to win 4–3 in the sudden death leg, three times having to break Woods's throw to stay in the match and seeing Woods miss one dart at bullseye for the match. Both players made a number of high finishes and consistent scoring, and it was very quickly labelled as one of the best matches ever played in the early stage of a World Championship. The win sent Wagner through to the quarter-final for the first time in his career. However, he was unable to replicate his form in the next round and was defeated 5–1 by number 1 seed
Tony O'Shea. Since 2012, Wagner has been competing in PDC-affiliated Scandinavian Darts Corporation (SDC). ==Controversy==