Just installed new dishwasher. Dishwasher fills, cleans and empties without issue. Hours later found water in bottom of dishwasher. Turns out when I empty say a pitcher of water into the sink, water trickles into the dishwasher from the inlet, not the drain. Faucet is not on when this happens. I cannot understand how this is even occurring. I then turn on dishwasher and cancel it, and it empties no problem from the drain.
Does your dishwasher have an "Air Gap" fitting installed? In some places this is a code requirement, but not everywhere, so installers in areas where it is not required will forego it because it costs extra and requires an additional hole in the sink, so installing it often means modifying the sink or even buying a new one (for example if it is cast iron).
Without an air gap, siphoning action of the water left in the drain tube can cause water in your sink to get sucked back into the dishwasher.
The alternative to an air gap shown in J. Raefield's answer is a "high loop".
Re-read your dishwasher installation instructions. The drain line must be routed so that at some point between the dishwasher outlet and the sink drain connection it is higher than the fill height of the sink.
This is to prevent sink water from entering your dishwasher plumbing, where is evidently finding the fill valve open.
Turns out Samsung dishwasher has a case break on side of dishwasher where drain water routes through. In case of drain blockage or whatever it is by design that water would then reroute in this case break and reenter dishwasher through inlet on side of dishwasher wall. Though I had a high loop coming off of my piping, it was on a lateral pipe between dual bowl sink. I had to attach DW drain to one of the sink drains, followed by p trap. Water is now "not" backing up and filling entire drain hose that was causing pressure rerouting into dishwasher. Posting in case others have this issue with water coming into inlet area of dishwasher caused by backflow.