Out of the Shanghai places available in Markham, I enjoy Ding Tai Fung's dumplings the most. Thin dumpling skin with juicy meatball inside. Their onion pancake isn't oily with a decent amount of onions unlike some where they taste only batter. Their gou choi dumplings are also flavourful and full of greens. Not the biggest fan of their stir fry meats but their fried rice and noodles are good quality and packed with flavour.
Lastly, customer service here is great compared to many other Chinese restaurants.
Try their sesame paste filled dessert dumplings, those are pretty good too. Not too sweet and has great sesame flavours as I believe they use real black sesame.