Non-namespace folder naming convention

Question

I'm working on a project in C# .NET (Visual Studio 2010) with a number of generated partial classes, metadata classes, etc. (if you know Entity Framework, you know what I mean)

My question pertains to the practice of correlating namespaces with directories, whereby each directory denotes a sub-namespace.

Now, I'd like to move the metadata classes into a sub-directory, purely for organizational purposes. Since partial classes must exist within the same namespace, the Metadata sub-directory can no longer denote a namespace (otherwise it'd break the partial classes) I'd be departing from the aforementioned practice; not a big deal, but I like sticking to a standard.

Is there a convention to denote that a given directory is purely organizational?

Off-hand, prefixing the directory name with "." (dot) or "_" (underscore) seems appropriate, the former more than the latter since it would result in an invalid namespace name.

---

@Pheonixblade9, something like this:

:
|
+- ProjectFolder/
|   +- App.config
|   +- Packages.config
|   +- ClassA.cs
|   +- ClassB.cs
|   +- ClassC.cs
|   +- ClassD.cs
|   +- Metadata/
|   |   +- ClassA.Metadata.cs  \
|   |   +- ClassB.Metadata.cs   \ These are the partial classes that shouldn't
|   |   +- ClassC.Metadata.cs   / be namespaced differently than their respective
|   |   +- ClassD.Metadata.cs  /  partials in the parent folder
:   :

Answer 1

Despite @JohanLarsson providing the correct answer for 2012+, I've opted for the . prefix on the directory:

:
+- ClassC.cs
+- ClassD.cs
+- .Metadata/
|   +- ClassA.Metadata.cs
|   +- ClassB.Metadata.cs
:   :

This renders the namespace name provided to classes created in that folder invalid. It's more of an implicit indicator than an explicit rule as I'd have preferred (and as @JohanLarsson's answer provides) but then again, I'm the sucker running 2010.

I'm still open to answers, and will gladly change acceptance to something better.

Answer 2

1. Select the folder in solution explorer
2. In properties set NameSpace Provider to false