to be fashionable
Examples
It used to be fashionable for authors to have their pictures taken with dogs, but the dogs always looked like models hired from an advertising agency, and probably were.
I would never stoop so low as to be fashionable.
For an idea ever to be fashionable is ominous, since it must afterwards be always old fashioned.
I'm not trying to be fashionable. Never was!
I think it's an old fashioned notion that fashion needs to be exclusive to be fashionable.
I always wanted to be fashionable.