As a general rule, beans which are really good for dry beans are at best "okay" for string beans (snaps). Beans which make good snaps are sometimes alright for dry beans, but as a general rule they don't produce as well for that purpose and/or they are difficult to thresh and extract from their dry pods.

Tell us what you like and someone here can make a suggestion. Off the top of my head, I suspect you would like Cherokee Trail of Tears, which is a black seeded pole bean (needs support because it gets tall). It produces lots of good snap beans, which mature to produce lots of good black beans. In my limited experience, this is one of the best all purpose beans. Cooper's Running Snap makes a pinto type bean and is also a good snap bean. Cooper's Running Snap is a pole type as well.

I grew royal purple last year. Doing that again this year.I liked the look and eating it freshly picked was great.

A few months ago i dumped some dries red kidney beans on one of my vegetable beds. Forgot to boil them to kill the beans. Now they keep popping up and i pull them up as they come. My mom asked why i throw them out when i should replant them for string beans. That's really what inspired the question. Is would any bean be able to grown for what most people consider string beans.

Okay. Yes, I doubt that kidney beans would be good as snaps, though, I don't have experience with them.

I concur with the comments by Macmex.

Dry beans seldom produce good snaps; the same fibrous pod that is desirable in dry beans (to protect the seed) generally makes them unpalatable as snaps. I've heard several gardeners mention that they found the very young pods of pinto beans edible as snaps... but with so many really good snap beans to choose from, I wouldn't recommend going that route.

You are far more likely to find a snap bean which is also good dry, or which makes good shellies. There are quite a few pole varieties in that category, and I've grown a couple dual-purpose bush varieties as well. Fresh shelly beans, IMO, are one of the best treats you can experience as a home gardener.