Dingman was ordained to the priesthood for the Diocese of Davenport on December 8, 1939, by Bishop Ralph Hayes in the Chapel of Our Lady of Humility at the North American College.

[2] Upon his return to Iowa, he taught at St. Ambrose Academy in Davenport from 1940 until 1943, when he became assistant chancellor of the diocese and Bishop Henry Rohlman's secretary.

[1] On April 2, 1968, Dingman was appointed as the sixth bishop of the Diocese of Des Moines by Pope Paul VI.

On October 4, 1979, Pope John Paul II visited the Diocese of Des Moines on the suggestion of Joe Hays, a farmer in Truro, Iowa, and on the invitation of Dingman.

[6] After landing at the Des Moines Airport, the pope visited the rural parish of St. Patrick near Irish Settlement.

On October 14, 1986, Pope John Paul II accepted Dingman's resignation as bishop of Des Moines due to poor health.