Stupid Array Tricks: Initializing an Array to a Certain Size

[tojo2000]

Okay, so I'm trying to use the SqlDataReader.GetValues() method, and
it wants me to pass it an array. The problem is that it wants the
array to be at least as large as the data that I want to put it in,
otherwise the data gets truncated.

I whipped this up, but it doesn't seem like the most efficient way:

foreach ($i in 0..($reader.FieldCount - 1)) {
$row += $null
}

Is there a better way to gin up an empty array of a specific size (a
contradiction, I know, but you know what I mean)?

[Shay Levy [MVP]]

PS > $arr = new-object object[] $reader.FieldCount

---
Shay Levy
Windows PowerShell MVP
http://blogs.microsoft.co.il/blogs/ScriptFanatic

t> Okay, so I'm trying to use the SqlDataReader.GetValues() method, and
t> it wants me to pass it an array. The problem is that it wants the
t> array to be at least as large as the data that I want to put it in,
t> otherwise the data gets truncated.
t>
t> I whipped this up, but it doesn't seem like the most efficient way:
t>
t> foreach ($i in 0..($reader.FieldCount - 1)) {
t> $row += $null
t> }
t> Is there a better way to gin up an empty array of a specific size (a
t> contradiction, I know, but you know what I mean)?
t>

[alexandair]

On Sep 8, 2:57 pm, Shay Levy [MVP] <n...@addre.ss> wrote:
> PS > $arr = new-object object[] $reader.FieldCount
>
> ---
> Shay Levy

> Windows PowerShell MVPhttp://blogs.microsoft.co.il/blogs/ScriptFanatic

>
> t> Okay, so I'm trying to use the SqlDataReader.GetValues() method, and
> t> it wants me to pass it an array.  The problem is that it wants the
> t> array to be at least as large as the data that I want to put it in,
> t> otherwise the data gets truncated.
> t>
> t> I whipped this up, but it doesn't seem like the most efficient way:
> t>
> t> foreach ($i in 0..($reader.FieldCount - 1)) {
> t> $row += $null
> t> }
> t> Is there a better way to gin up an empty array of a specific size (a
> t> contradiction, I know, but you know what I mean)?
> t>

You could also use a static method CreateInstance of the Array class
(hat tip to /\/\o\/\/):

PS> $arr = [array]::CreateInstance([object],$reader.FieldCount)

In some cases, this approach is also good when you want to control the
array's element type:

PS>$a = [array]::CreateInstance([datetime],10)
PS>$a[0] = "test"

Array assignment to [0] failed: Cannot convert value "test" to type
"System.DateTime". Error: "The string was not recognized as a valid
DateTime. There is a unknown word starting at index 0.".
At line:1 char:4
+ $a[0 <<<< ] = "test"

-aleksandar
http://powershellers.blogspot.com

[tojo2000]

Thanks guys. I knew there was a way to do that, but I couldn't find
it.

[Hal Rottenberg]

tojo2000 wrote:
> Is there a better way to gin up an empty array of a specific size (a
> contradiction, I know, but you know what I mean)?

This came up on #powershell some time ago and I blogged a really short solution.
Then Bruce Payette followed up with more info which was awesome, so click the
link to see that.

http://halr9000.com/article/430

method 1:

$array = ,0 * 20

method 2:

$array = @(0) * 20

--
Author, Tech Prosaic blog (http://halr9000.com)
Webmaster, Psi (http://psi-im.org)
Community Director, PowerShellCommunity.org
Co-host, PowerScripting Podcast (http://powerscripting.net)