To hold the office of county commissioner, sheriff, county attorney, county treasurer, register of deeds, or register of probate, a person must have a domicile in the county for which he is chosen. In addition, to hold the office of county commissioner in the counties of Rockingham, Belknap, Grafton, Merrimack, Hillsborough, Cheshire, Sullivan, Coos, and Carroll, a person must have a domicile in the district from which he is elected at the time of his election.