How can I return a byte array (rather than an Object array) from a PowerShell function

Question

I am trying to create a function that return a a byte array ([Byte[]]).

However, when I use the function and assign the returned value to a variable, the type of the variable is an array of objects ([Object[]]).

function make-byteArray() {
  [OutputType([Byte[]])]

   [byte[]] $byteArray = new-object byte[] 2
   $byteArray[0] = 0
   $byteArray[1] = 1

   write-host "type of byteArray: $($byteArray.GetType().FullName)"

   return $byteArray
}

$x = make-byteArray
write-host "type of x: $($x.GetType().FullName)"

I am puzzled why that is and would like to know what I can do to force the function to return a byte array.

Theo · Accepted Answer · 2020-04-26 11:45:14Z

7

Just add the unary comma , before the returned $byteArray like this:

return ,$byteArray

Return:

type of byteArray: System.Byte[]
type of x: System.Byte[]

This will wrap the returned array inside another, one-element array. When an array is returned from a function, PowerShell 'unrolls' that and in this case, it unrolls the wrapper array, leaving the byte array inside.

answered Apr 26, 2020 at 11:45

Theo

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avarice · Accepted Answer · 2020-04-26 12:08:53Z

2

You can use Write-Output Instead of return:

Write-Output $bytearray -NoEnumerate

Return statement always unpacks the return object so it gets a type of System.Object[]

answered Apr 26, 2020 at 12:08

avarice

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