Argument Modifiers: 'ref', 'out', 'params' and 'this'

Some c-sharp devs must slink through their whole skanky career, utterly ignorant about argument modifiers.

There's usually a way to avoid thinking about them: if you're willing to write a lot more code and have your existing stuff crash and get patched many more times.

The best known 'argument modifier' is probably 'ref' -- and it's purpose is pretty damn powerful. I assume you know its purpose: but just imagine you've just gone from a state of not knowing what the ref param modifier does, to a state where you know what it does. Think of all the things you couldn't do before that are now open to you. Hold that thought.

I'd say that I use 'out' possibly a little more often than I use 'ref' -- yet I wouldn't rank it quite so high on the 'mind-blowing' stakes. The 'params' argument modifier is certainly mind-blowing, if you've never used it before. It gives the language a whole big chunk of 'affordance' -- allow you to achieve, very simply, ranges of motion that are otherwise almost inachievable.

But what about the 'this' modifier.

I'd wager that 70% of the C sharp devs out there haven't yet parsed the 'this' argument modifier.

And when they do -- i hope to see the nightsky light up with the colourful spectacle of a hundred thousand minds noisily exploding under the power of extension methods.

If you're part of that sad 70%, go now and learn how to implement an extension method or ten.

'params' is indeed woefully underused, though I'm not sure why. I see 'ref' sometimes, often used where 'out' should have been. And you can't really blame people for missing out out 'this', as that version of the language isn't exactly *released* yet...

The 'this' modifier is mindblowing. 'params' is not. It's been around since old-style VB in an almost identical form and the concept for even longer. The reason the C calling convention (parameters pushed onto the stack in reverse order, caller cleans up) was invented was to support this. It really is nothing special.

I also like 'ref' and 'out', especially the distinction between the two, though it would be nice if there were a way to pass a null reference (though then we're back where we started with pointer parameters... not that I have a problem with that either).

Erm, So what is so special about the keywword "this".

I suppose you aren't talking about this in the way that it reduces the scope to the object you are programming in cause the feature hasn't been releases I read in the comments.

Can you clarify this?

I tend to avoid out/ref, as I feel a method's results should be returned as an assignment, not via its parameters.

A lot of out/ref parameters just confuse me. Add a return value to the mix, and I usually fail to understand what the method is supposed to do.

I know that you are talking mainly about "this" but isn't using structures for multiple return values is better than using multiple out?

With the "this" keyword and some of the other changes (like the implicit typing) it seems that C# is moving slowly and crabwise from Java to JavaScript.

'ref' is essential. FxCop will complain if you have the effrontery to use 'out', and suggests that you find another way. 'this' is still in the future (for me at any rate since I usually avoid betas and CTPs).

>FxCop will complain if you have the
>effrontery to use 'out', and suggests
>that you find another way

really? wow.

The danger there is that someone will simply change out to ref, thus forcing users to initialise the variable and pass in a reference when the param is always created within the given method.

I hate examples where the best way to avoid a warning is to write uglier code.

I think the use of 'out' as in TryParse is decent. But also -- i just googled the topic and wow some people don't like 'out' at all.

Here's a codeproject link

http://www.codeproject.com/useritems/alternative_2_out_keyword.asp

Leon,

Here's the Microsoft FxCop rule regarding out parameters:-

http://msdn2.microsoft.com/en-us/library/ms182131(VS.80).aspx

Note the Community Content at the bottom, which fits in with your comment on TryParse.

Argument Modifiers: 'ref', 'out', 'params' and 'this'

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