Where and how to use the EXTERN

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Victor - 07 May 2007 19:49 GMT

Hi,

Am a novice in c#, tell me about how and where i can use "Extern" Keyword
with some good example

Thansk

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Chakravarthy - 07 May 2007 19:55 GMT

Dont hesitate while asking any question.. this is public world, ask any thing
you want to learn, dont hesitate.

Secondly, extern key word is used when you wanted to import any assembly out
side your scope, ie., not within the application.

Inother words, the dlls which are already created and you have a situation
to use them at run time, then take the assistance from Extern key word

Exmaple from MSDN

[DllImport("avifil32.dll")]
private static extern void AVIFileInit();

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> Hi,
>
> Am a novice in c#, tell me about how and where i can use "Extern" Keyword
> with some good example
>
> Thansk

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Jon Skeet [C# MVP] - 07 May 2007 20:26 GMT

> Dont hesitate while asking any question.. this is public world, ask any thing
> you want to learn, dont hesitate.
>
> Secondly, extern key word is used when you wanted to import any assembly out
> side your scope, ie., not within the application.

It's almost never used for *assemblies* (which are managed code) - it's
almost alwyas used for using functions in unmanaged libraries.

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Jon Skeet - <skeet@pobox.com>
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Brian Schwartz - 08 May 2007 18:48 GMT

A common use of it is for the Windows API. I have a class that contains
declarations like this:

internal static class API
{
[DllImport("user32.dll")]
internal static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, UIntPtr
wParam, IntPtr lParam);
}

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Brian Schwartz
FishNet Components
http://www.fishnetcomponents.com
Fish Grid .NET Light: Powerful Layouts for Small Datasets

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Where and how to use the EXTERN

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