Don't know about containers. Salix like moist soils and send roots down to find water. So, I would have thought not?

Agree with Bulbaholic, a container cannot meet all its water needs even if you assiduously water it. I have never seen a containerised Salix last!

Mine has been in container for 6yrs and does well.

I shall post a photo later.

Depends which variety of Salix you've got - Kilmarnock Willow, the shorter ones, can be kept in large containers for a few years. The taller standards don't keep so well in pots for as long though. The other one that does all right for a few years in large enough pots is Salix Hakuro-Nishiki, sometimes called flamingo Salix. Both varieties will need a fair amount of watering, they do not really like to dry out completely, preferring well drained but moist soil, and should be potted on into larger containers as and when necessary (possibly yearly or bi yearly)