Milan to Lugano day trip

Yes I have done this. It's very easy, you can stop in Como on the way back for dinner. I climbed the alplette Mt Bre. If I recall I never even changed money.

Thanks Tom. Is it one train or is a transfer required?

If you take one of the Eurocity trains that go every 2 hours, they are direct.

dp,

Yes, you can absolutely take a day trip to Lugano. As I recall, travel time is only a very short one hour each way. The rail station in Lugano is located above the town, so you can either walk or take the Funicular down. It's a very walkable city, and a stroll along the lakeside from Lugano to Paradiso is very nice. If you want to take the Funicular up to Monte San Salvatore, that's located in Paradiso.