Out of habit I tend to put classes/structs/enumerations in separate files when not nested.
For delegates, it seems like overkill to create a seperate file for a one liner:
public delegate string MyDelegateThatIsNotNestedInAnyClass ( string par );
I usually add it to the bottom of the most closely related class file. I was just wondering what other people do?
I usually add it to the .cs file of the class which implements the delegate function (at the namespace level). If there are several of these, I put it in a separate file.
If I know for sure that only one class will implement the delegate function, I nest it in the implementing class.
I personally add it before a closely related class definition. I make good use of namespaces, though, so I don't pollute!
If it's closely related enough to belong in the same file as the class, then you can probably justify nesting it in the class. Then you'll have no trouble remembering which class file it's in.
If there's no single class that's an obvious choice to nest in, creating the one-line file is probably worthwhile since you'll never waste time trying to remember which class file you decided to put it in.