I don't recall why I started asking this question at interviews, I don't actually think it tells me anything other than whether the interviewee knows the difference between string and String and now I find that I can't stop myself from asking it.
I just want somebody to give me the right answer, one person, just one person would do.
Thus far, I've asked this question at eight interviews, yes, I know a pitifully small sample size, but still I would've expected to have found somebody who was aware of the difference or lack thereof.
It's not like all interviewees have been fresh out of uni, in fact only one has been.
By far the most common answer (~90%) is :
String is class
For those of you wondering, what the difference is: There is none
What a bastard, right?
string is just an alias of System.String.