Difference between out and [Out]

[=?Utf-8?B?RGF2ZQ==?=]

I have been doing a lot of PInvoke calls using signatures published on
www.pinvoke.net. I notice that where out parameters are involved, sometimes
the signature uses 'out' and sometimes '[Out]'. I have discovered that using
the wrong one causes nasty things to happen, but I can't work out what the
difference is, and when one should be used and when the other (luckily I have
not yet had to work out my own signatures for PInvoke calls, but I may have
to one day)
--
Dave

[Mattias Sjögren]

>I have been doing a lot of PInvoke calls using signatures published on

>www.pinvoke.net. I notice that where out parameters are involved, sometimes
the signature uses 'out' and sometimes '[Out]'. I have discovered that using
the wrong one causes nasty things to happen, but I can't work out what the
difference is, and when one should be used and when the other (luckily I have
not yet had to work out my own signatures for PInvoke calls, but I may have
to one day)

out is equivalent to using [Out] ref.

Both ref and out change the way the parameter is passed (by reference
ratehr than by value).
Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[=?Utf-8?B?RGF2ZQ==?=]

Thanks. I understand out and ref. Can you explain what [Out] actually is,
syntactically?
--
Dave
"Mattias Sjögren" wrote:

I have been doing a lot of PInvoke calls using signatures published on
www.pinvoke.net. I notice that where out parameters are involved, sometimes
the signature uses 'out' and sometimes '[Out]'. I have discovered that using
the wrong one causes nasty things to happen, but I can't work out what the
difference is, and when one should be used and when the other (luckily I have
not yet had to work out my own signatures for PInvoke calls, but I may have
to one day)

out is equivalent to using [Out] ref.

Both ref and out change the way the parameter is passed (by reference
ratehr than by value).
Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Jon Skeet [C# MVP]]

On Nov 14, 9:03 am, Dave <[e-mail]:

Thanks. I understand out and ref. Can you explain what [Out] actually is,
syntactically?

It's an attribute - OutAttribute, to be specific.

Jon

[=?Utf-8?B?RGF2ZQ==?=]

Doh! Of course it is. Sorry. Attributes are one aspect of the C# language
I've never really got my head round, I must read up on them more carefully.
Thanks for the quick response.
--
Dave
"Jon Skeet [C# MVP]" wrote:

On Nov 14, 9:03 am, Dave <[e-mail]:

Thanks. I understand out and ref. Can you explain what [Out] actually is,
syntactically?

It's an attribute - OutAttribute, to be specific.

Jon