IDE0005 error: using directive is unnecessary

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I am revising a solution w/ multiple projects. I added a new project (or namespace), named as _NewProj. In an existing .cs, I added

using _NewProj

However, I received IDE0005 error: Using directive is unnecessary.
How to resolve it? Thanks.

What I have tried:

IDE0005 error: Using directive is unnecessary

Posted 23-Apr-24 4:17am

s yu

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PIEBALDconsult 23-Apr-24 10:46am

Really an error? Or a warning treated as an error?
What happens if you comment it out?
Bear in mind that no using directives are ever strictly necessary.

s yu 23-Apr-24 10:56am

I do need to call the functions in the NewProj namespace. If it is commented out, all of the function calls are errored.

Dave Kreskowiak 23-Apr-24 12:04pm

So the using directive has the namespace as "_NewProj", and you're saying the namespace is "NewProj". Those are two different namespace names and are not interchangeable.

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OriginalGriff · Answer 1 · 2024-04-23T19:44:00

Name in C# - variables, methods, properties, namespaces, everything which can be named - are precise: they have to match exactly. That means underscores, the case, and the letters must be identical for two names to "match".
For example, "Count" is not the same as "count", "hello" is not the same as "he11o", and "ItemsCount" is not the same as "Items_Count".

If you are getting the style warning IDE0005 it means that the namespace you referenced in the using directive is not actually used in your code: no items you use are from that namespace, or such items are prefixed with that namespace because there are two ways to reference an item external to the current class:
1) With a using directive

C#

using MyNamespace;
...
   ItemInMyNamespace x = new ItemInMyNamespace();

Or
2) By fully qualifying the name:

C#

//using MyNamespace;
...
   MyNamespace.ItemInMyNamespace x = new MyNamespace.ItemInMyNamespace();

The two forms are interchangeable: you can have a using directive and still fully qualify the name:

C#

using MyNamespace;
...
   MyNamespace.ItemInMyNamespace x = new MyNamespace.ItemInMyNamespace();

If that is coming up as an error by the way, then congratulations! You have the VS option "treat warnings as errors" enabled which is an excellent way to catch problems before they get to run time! :thumbsup: