Powershell Bool returns Array

Question

I'm tryng to return $true or $false from a function, and I get an array . If I remove the listBox messages it works as expected. Does anyone know why?

function TestEmptyFields()
{
  $empty= $false

  $listBox1.Items.Add("Testing fields")

  if ($txtPrtName.get_text()-eq "")
  {
    $listBox1.Items.Add("Empty name")
    $empty= $true
  }
  elseif ($txtPrtIP.get_text() -eq "")
  {
    $listBox1.Items.Add("Empty Ip")
    $empty= $true
  } 
  else 
  {
    $empty= $false
  }

  $listBox1.Items.Add($txtPrtName.get_text())
  $listBox1.Items.Add($txtPrtIP.get_text())

  return $empty
}

But it works fine like this:

function TestEmptyFields()
{
  if($txtPrtName.get_text()-eq "")
  {
    return $true
  }
  elseif ($txtPrtIP.get_text() -eq "")
  {
    return $true
  }
  else
  {
    return $false
  }
}

Did you try returning the value earlier? i.e. not writing $empty= $true but directly return $true instead? Apart from that it is not that easy to help you debug this if we do not have the parts where $txtPrtName, $txtPrtIP and $listBox1 get assigned/declared. I would also recommend you not to process global variables in a function but make them parameters of that function. — DrCopyPaste
– DrCopyPaste, Commented Sep 20, 2013 at 7:35
function TestEmptyFields() { if($txtPrtName.get_text()-eq "") { return $true }elseif($txtPrtIP.get_text() -eq "") { return $true }else{ return $false } } — user2798062
– user2798062, Commented Sep 20, 2013 at 7:42
can you include the code that sets up the variables that you are testing in your function? or make them parameters? — DrCopyPaste
– DrCopyPaste, Commented Sep 20, 2013 at 7:46

Anthony Neace · Accepted Answer · 2013-09-20 07:46:25Z

6

In powershell return $empty is functionally equivalent to $empty ; return -- that behavior was implemented to make things easier for people with a background in C-style languages, but you're actually returning more than you think! The listboxes return content as well. In fact, anything that isn't assigned to a variable or otherwise has its output nullified will reach the output stream. To fix this, try casting listbox to [void] like so:

[void] $listBox1.Items.Add("Testing fields")

It probably wouldn't hurt to review this TechNet guide on proper usage of Listboxes in the context of a form, either.

answered Sep 20, 2013 at 7:46

Anthony Neace

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2 Comments

manojlds Over a year ago

Plug, if you don't mind - stacktoheap.com/blog/2013/06/15/…

oscar Over a year ago

"anything that isn't assigned to a variable or otherwise has its output nullified will reach the output stream". Is this concept a Microsoft design decision for some known reason? It seems to me more an annoyance, prone to develop buggy functions.

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