CODEWITHSUNDEEP
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Martin Fehrs
Martin Fehrs

Reputation: 1091

calling replace method on system.array

I'm new to the .Net World and Powershell. I have the following code:

$e = "A","A","A","B","A","B","A","A"

write-output $e.Replace("B", "C")

it works and prints

A
A
A
C
A
C
A
A

But I cannot find a Replace Method for system.array only for system.string. Why is it working?

Upvotes: 1

Views: 172

Answers (2)

Ansgar Wiechers
Ansgar Wiechers

Reputation: 200283

The replacement is working because you're running PowerShell v3 or newer. In PowerShell v3 Microsoft added a feature called member enumeration, which makes PowerShell invoke a method or property on all elements of an array if the array object itself doesn't have such a method or property.

If you run PowerShell v2 (e.g. by invoking powershell.exe -version 2) and run your code in that instance you'll get the following error:

Replace : Method invocation failed because [System.Object[]] doesn't contain
a method named 'Replace'.
At line:1 char:24
+ write-output $e.Replace <<<< ("B", "C")
    + CategoryInfo          : InvalidOperation: (Replace:String) [], RuntimeException
    + FullyQualifiedErrorId : MethodNotFound

Upvotes: 3

Bernard Moeskops
Bernard Moeskops

Reputation: 1283

First of all, you don't need the "Write-Output"-part. But it works because you replace strings within the array for other strings.

Let me demonstrate:

$e = "A","A","A","B","A","B","A","A"
foreach($obj in $e){
    $obj.GetType()
}

This outputs (only posted first 2 lines):

IsPublic IsSerial Name                                     BaseType                                                                                                                                                                                              
-------- -------- ----                                     --------                                                                                                                                                                                              
True     True     String                                   System.Object                                                                                                                                                                                         
True     True     String                                   System.Object

Upvotes: 0

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