Question

More a question out of curiosity than anything, but why does C# define two different “purposes” for the keyword using? On one hand, it’s a directive…

used to create an alias for a
namespace or to import types defined
in other namespaces.

On the other, it’s a statement which…

defines a scope, outside of which an
object or objects will be disposed.

To me, it seems like different uses for the same keyword, but maybe I’m missing something. Is there a reason why this keyword takes on two different purposes? Or, are both of these purposes, deep down in the belly of the compiler, really the same thing?

Answer 1

I asked Eric Lippert the same question on his blog a few years ago here (see the first comment).

His response was:

This is a tricky point of language
design; when one keyword is used to
represent two completely different
concepts, it can be confusing. But
introducing a new keyword per concept
makes the language feel a bit bloated.
I personally would have chosen
“imports” or some such syntax for the
directive form to ensure that it is
not confused with the statement form,
but I understand that its a judgment
call.

We were designing a feature for C# 4.0
that got cut which was yet another
form of “partial” class; basically, a
way to share attribute metadata
between the machine-generated and
user-generated halves of a partial
class. I pushed back on using the
keyword “partial” for the feature
because we would then have had THREE
subtly different meanings for
“partial” in C#, which I felt was two
too many. (I was advocating adding
another conditional keyword
“existing”. Unfortunately the point
ended up moot since the feature was
cut for lack of time.) — Eric

For those who don’t know who Eric is, he’s a developer for the C# compiler team.