I have both US green card and Canada Maple card. I did landing on early 2008 and never lived in Canada after that. I applied SSN of Canada but they never mail me. Now I want to go to a conference held in Toronto, my questions are: 1. do I need a visa to Canada if I do not have Maple card? 2. Is there any problem entering Canada due to my Maple card? 3. Will Canadian custom find trouble with me? Will they ask me to abandon Maple card? I am very confused. Should I go? Thank you very much,