Hafner is the Associate Dean for Collection Services at McGill University in Montreal, where he manages staff who are responsible for collection development, receiving, processing, cataloguing, metadata and interlibrary loans and where he has worked in various roles since 2004. He is the past chair of the IFLA Acquisition and Collection Development Committee, a Vice-President for the International Association of Music Libraries and he is on the American Library Association committee for Chief Collection Development Officers of Large Research Libraries. He is a member of the HathiTrust Rights and Access Working Group and the OCLC e-Resources Advisory Group, and has recently completed the Association for Research Libraries Leadership Fellows Program.