array of interface?

17 Jan 2006 7:14 PM

haroldsphsu

Hi,

I understand that I cannot create an instance of an interface, but why
is it ok to do the following? What is it creating?

foo = New System.ComponentModel.IEditableObject(10) {}

whereas the following will get a compiler error ('New' cannot be used
on interface):

foo = New System.ComponentModel.IEditableObject(10)

Thanks,
Harold

17 Jan 2006 7:30 PM

Mattias Sjögren

>What is it creating?

An 11-element array of the interface type, just like your subject
says.

Mattias

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Mattias Sjögren [C# MVP] mattias @ mvps.org
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17 Jan 2006 7:41 PM

haroldsphsu

But why is it an error if I don't specify the empty array element
initializer?

17 Jan 2006 7:49 PM

haroldsphsu

Sorry, I think I got it. Without the array initializer, it's not
actually an array I'm creating.

17 Jan 2006 7:47 PM

Herfried K. Wagner [MVP]

<haroldsp***@gmail.com> schrieb:

> I understand that I cannot create an instance of an interface, but why
> is it ok to do the following? What is it creating?
>
> foo = New System.ComponentModel.IEditableObject(10) {}

An array with items of type 'IEditableObject' containing 11 elements with
indices 0 through 10.

> whereas the following will get a compiler error ('New' cannot be used
> on interface):
>
> foo = New System.ComponentModel.IEditableObject(10)

In this case the curly braces are required to make the compiler aware that
an array should be created instead of calling a non-existing constructor.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

17 Jan 2006 7:52 PM

haroldsphsu

Thanks Herfried and Mattias!