One class per file rule in .NET? [closed]

Question

I hate it when people think in absolutes and say you should never do this or that with something subjective and nit-picky like this, as if we all need to conform to someones stupid idea of right and wrong. Bottom line: having more than one class per file is totally fine if it makes sense. By makes sense I mean things like:

1. Makes the code easier to digest and maintain
2. Makes the solution less annoying (scrolling through countless unnecessary files) and less slow
3. The dev team is okay with it as a local coding practice

A really good example of why I may want multiple classes per file:

Say I've got a few dozen custom exception classes, each one is a 4 liner, I could have a separate file for each one or I could group the exceptions and have a file per group. For me what seems the most rational/pragmatic approach is to group them, and just have a few files, because it's more efficient time/coding wise (I don't have to right-click -> Add Class, rename, 50 times), it keeps the solution less cluttered and better performing.

One class per file also gives you a better idea of what each check in is changing without looking at the diffs of the file.

static bool GeneralRuleShouldBeFollowed(IGeneralRule rule, IUseCase useCase)
{
    return (rule.Overhead(useCase) 
            < My.PersonalThresholds.ConformismVsPracticality);
}

I sometimes group more than one class within a file if they are tightly coupled and at least one of them is very small.

General 'best practice' is to have one file per class.