Best way to check if an PowerShell Object exist

Question

I am looking for the best way to check if a Com Object exists   Here is the code that I have  I d like to improve the last line    ie   New-Object -ComObject InternetExplorer Application  ie Navigate  http   www stackoverflow com    ie Visible    true   ie -ne  null  Are there better options

User · Answer

What all of these answers do not highlight is that when comparing a value to $null, you have to put $null on the left-hand side, otherwise you may get into trouble when comparing with a collection-type value. See: https://github.com/nightroman/PowerShellTraps/blob/master/Basic/Comparison-operators-with-collections/looks-like-object-is-null.ps1

$value = @(1, $null, 2, $null)
if ($value -eq $null) {
    Write-Host "$value is $null"
}

The above block is (unfortunately) executed. What's even more interesting is that in Powershell a $value can be both $null and not $null:

$value = @(1, $null, 2, $null)
if (($value -eq $null) -and ($value -ne $null)) {
    Write-Host "$value is both $null and not $null"
}

So it is important to put $null on the left-hand side to make these comparisons work with collections:

$value = @(1, $null, 2, $null)
if (($null -eq $value) -and ($null -ne $value)) {
    Write-Host "$value is both $null and not $null"
}

I guess this shows yet again the power of Powershell !

User · Answer

I had the same Problem  This solution works for me    Word    null  Word    System Runtime InteropServices Marshal   GetActiveObject  word application   if   Word -eq  null         Word   new-object -ComObject word application     https   msdn microsoft com de-de library system runtime interopservices marshal getactiveobject v vs 110  aspx

User · Answer

Type-check with the -is operator returns false for any null value  In most cases  if not all   value -is  System Object  will be true for any possible non-null value   In all cases  it will be false for any null-value    My value is nothing if not an object

User · Answer

In your particular example perhaps you do not have to perform any checks at all  Is that possible that New-Object return null  I have never seen that  The command should fail in case of a problem and the rest of the code in the example will not be executed  So why should we do that checks at all   Only in the code like below we need some checks  explicit comparison with  null is the best      we just try to get a new object  ie    null try        ie   New-Object -ComObject InternetExplorer Application   catch       Write-Warning         check and continuation if   ie -ne  null

User · Answer

I would stick with the  null check since any value other than     empty string   0   false and  null will pass the check  if   ie

User · Answer

You can also do   if   ie          Do Something if  ie is not null

User · Answer

Incase you you re like me and you landed here trying to find a way to tell if your PowerShell variable is this particular flavor of non-existent      COM object that has been separated from its underlying RCW cannot be   used    Then here s some code that worked for me   function Count-RCW    ComObject  ComObj      try  iuk    System Runtime InteropServices Marshal   GetIUnknownForObject  ComObj      catch return 0     return  System Runtime InteropServices Marshal   Release  iuk -1     example usage    if  Count-RCW  ExcelApp  -gt 0   System Runtime InteropServices Marshal   FinalReleaseComObject  ExcelApp     mashed together from other peoples  better answers    RCW  amp  reference counting when using COM interop in C  RCW Reference Counting Rules    COM Reference Counting Rules    COM object that has been separated from its underlying RCW cannot be used    with  NET 4 0   and some other cool things to know    COM object that has been separated from its underlying RCW cannot be used Custom Marshaling Advanced COM Interoperability

[powershell] Best way to check if an PowerShell Object exist?

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