Assuming that you already hold a EASA B2 licence, there is no specific B2 type training course available for the DA42 model.
The aircraft will fall under a B2 Full 'Group 3 aircraft' rating.
In the UK this can be obtained by providing logbook experience on the aircraft, and sitting an oral exam with an inspector. Depending on your national authority I imagine there will be a very similar process. It would be worth getting in touch with your NAA to confirm this.
In terms of training on the aircraft, Diamond do offer airframe/engine courses for B1 engineers. However, if you are looking for B2 training then the best option would be to attend the G1000 course at Garmin. It won't give you any type rating, but it will help to ensure you are familiar with the G1000 avionics system fitted on the DA42.
Hope this helps.