Some textbook publishers provide questionbanks along with software such as ExamView or TestGen. These programs are primarily designed for creating paper tests, but can export in online formats. Neither program directly supports D2L, but in most cases exporting in Blackboard format will work. There may be some occasional incompatibilities, since D2L and Blackboard implement some question types differently.
An alternative solution for publisher test banks is using Respondus and their Test Bank Network. Access codes must be requested through your publisher representative.