Why remove unused using directives in C#?

There are a few reasons you'd want to take them out.

• It's pointless. They add no value.
• It's confusing. What is being used from that namespace?
• If you don't, then you'll gradually accumulate pointless using statements as your code changes over time.
• Static analysis is slower.
• Code compilation is slower.

On the other hand, there aren't many reasons to leave them in. I suppose you save yourself the effort of having to delete them. But if you're that lazy, you've got bigger problems!

I would say quite the contrary - it's extremely helpful to remove unneeded, unnecessary using statements.

Imagine you have to go back to your code in 3, 6, 9 months - or someone else has to take over your code and maintain it.

If you have a huge long laundry list of using statement that aren't really needed, looking at the code could be quite confusing. Why is that using in there, if nothing is used from that namespace??

I guess in terms of long-term maintainability in a professional environment, I'd strongly suggest to keep your code as clean as possible - and that includes dumping unnecessary stuff from it. Less clutter equals less confusion and thus higher maintainability.

Marc

Less options in the IntelliSense popup (particularly if the namespaces contain lots of Extension methods).

Theoretically IntelliSense should be faster too.

Code compiles quicker.