Bug with Array.CreateInstance() when lower bound > 0

[Gianluca]

If you create an array using Array.CreateIns tance() and use a lower bound >
0, you apparently get an array of the wrong type.

int[] lenghts = new int[] {1};
int[] lowerBounds = new int[] {1};
string[] ar = (string[])Array.CreateIn stance(typeof(s tring), lengths,
lowerBounds);

Throws an InvalidCastExce ption because "string[*]" cannot be casted to
"string[]".

int[] lenghts = new int[] {1};
int[] lowerBounds = new int[] {0};
string[] ar = (string[])Array.CreateIn stance(typeof(s tring), lengths,
lowerBounds);

This works fine. The only difference in the lower bound.

int[] lenghts = new int[] {1,1};
int[] lowerBounds = new int[] {1,1};
string[,] ar = (string[,])Array.CreateIn stance(typeof(s tring), lengths,
lowerBounds);

Even this work fine. The difference is the number of dimensions. So the
problem cannot be just the lower bound 0 because in this case (and with
more dimensions too) it works well.

Everything works well in .NET 1.1. So it's apparently a bug introduced in
..NET 2.0.

Has anyone seen this before? And what is "string[*]"?

Regards,
Gianluca

[Jon Skeet [C# MVP]]

Re: Bug with Array.CreateIns tance() when lower bound > 0

Gianluca <gianluca@nospa m.comwrote:

If you create an array using Array.CreateIns tance() and use a lower bound >
0, you apparently get an array of the wrong type.

Well, sort of.

Internally, .NET has two types of array - "vectors" (single-
dimensional, 0-based) and more general arrays.

When C# uses a single-dimensional array, it *assumes* it's one of these
"vector" types and that's what it really casts it to.

If you need to use a single-dimensional array with a non-zero lower
bound in C#, you need to access it using the Array class (and IList
etc).

Everything works well in .NET 1.1. So it's apparently a bug introduced in
.NET 2.0.

Hmm... I thought I'd seen exactly the same behaviour in 1.1...
unfortunately I can't easily test it any more.

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

[Gianluca]

Re: Bug with Array.CreateIns tance() when lower bound &gt; 0

Yep. I know about the internal difference between the vector and the array.
And you are right that it doesn't work with .NET 1.1 as well. I was testing
MD arrays and it also works if you cast it in the immediate window.

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:MPG.1fca28 89585af06a98d62 a@msnews.micros oft.com...

Gianluca <gianluca@nospa m.comwrote:

If you create an array using Array.CreateIns tance() and use a lower

bound >

0, you apparently get an array of the wrong type.

>
Well, sort of.
>
Internally, .NET has two types of array - "vectors" (single-
dimensional, 0-based) and more general arrays.
>
When C# uses a single-dimensional array, it *assumes* it's one of these
"vector" types and that's what it really casts it to.
>
If you need to use a single-dimensional array with a non-zero lower
bound in C#, you need to access it using the Array class (and IList
etc).
>

Everything works well in .NET 1.1. So it's apparently a bug introduced

in

.NET 2.0.

>
Hmm... I thought I'd seen exactly the same behaviour in 1.1...
unfortunately I can't easily test it any more.
>
--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too