[psyc]

That's where every Visual Studio dev will see them used, because it's been a VS pattern since the beginning. But I create them manually often enough. Overall I use them sparingly, but there are cases where you definitely want a set of things in one class for code-organization, but still want to think of them as different modules for human-organization.

[Gibbon1]

I did that once where I had a complicated class with a docile public API that controlled a not so docile long running threaded 'machine' of sorts. Having them in two files made thinking about stuff easier.

[tigershark]

If you want to think of them as different modules then most likely they should be completely separated entities. Why on earth you would want something completely different to live in the same class? It is just screaming that it wants to be a separate class. Namespaces are the correct tool for code organisations, certainly not partial classes.

[psyc]

It's very interesting that you were able to see my use cases and come to this conclusion...

[tigershark]

Regardless of the use case this is what the official documentation says about namespaces:

The namespace keyword is used to declare a scope that contains a set of related objects. You can use a namespace to organize code elements and to create globally unique types.

And about partial classes:

There are several situations when splitting a class definition is desirable: When working on large projects, spreading a class over separate files enables multiple programmers to work on it at the same time. When working with automatically generated source, code can be added to the class without having to recreate the source file. Visual Studio uses this approach when it creates Windows Forms, Web service wrapper code, and so on. You can create code that uses these classes without having to modify the file created by Visual Studio.

As you can see partial classes are not the right tool to organise code.

[psyc]

How would you propose to split a struct that has a single data member? Say, a struct where the only data is one unsigned short?

Also, "regardless of the use case" ? I barely know how to respond to that. Have a little imagination.