I am travelling to Bangladesh in mid-may and I booked my ticket already. I am going through Toronto,Canada. So I came to know that I have to have a transit visa for that. So I have 20 days at most in my hand for that. Is that possible to get a transit visa for Canada within 20 days? Is there any way out to expedite the processing?
Official processing times are at http://www.cic.gc.ca/english/information/times/ (select Visiting -> Visitor Visa). Make sure you actually need a visa first (as opposed to, say, just an electronic travel authorization - it depends on your country of citizenship). I don't know which country you're from, but for many countries the processing times are short and certainly fit in 20 days (but remember that if you don't live in a city with a visa processing center, you also need to add courier times to deliver your passport to the center and back to you). Also, from my personal recent experience (helping with 2 visa applications in Russia), processing was much faster than what it said on the website.