Sell somebody down the river

Meaning:

• If you do something which harms someone or disappoints someone's expectations.
• If you do something that hurts someone who trusted you.  
• If you betray somebody  in order to get an advantage for yourself.

Example sentence:

We were a good team and I trusted him like nobody else but once he found out he could get the contract for himself he immediately sold me down the river.



Questions for you to answer:

1. Have you sold anybody down the river?
2. Have you ever been sold down the river?
3. The English also say: 'to send somebody up the river'. Would you say that these two idioms have the opposite meaning? Consult a dictionary if necessary.