PowerShell AppPool Assignment Problems

The WebAdministration module has a Function called IIS:. It essentially acts like a drive letter or an uri protocol. Its really convenient and makes accessing appPool, site information, and ssl bindings easy.

I recently noticed two problems with assigning values through the IIS: protocol or the objects which is works with:

StartMode Can’t Be Set Directly

For some reason, using Set-ItemProperty to set the startMode value directly throws an error. But, if you retrieve the appPool into a variable and set the value using an = operator, everything works fine.

# https://connect.microsoft.com/PowerShell/feedbackdetail/view/1023778/webadministration-apppool-startmode-cant-be-set-directly
ipmo webadministration

New-WebAppPool "delete.me"

Set-ItemProperty IIS:\AppPools\delete.me startMode "AlwaysRunning" # throws an error

$a = Get-Item IIS:\AppPools\delete.me
$a.startMode = "AlwaysRunning"
Set-Item IIS:\AppPools\delete.me $a # works

Here is the error that gets thrown:

Set-ItemProperty : AlwaysRunning is not a valid value for Int32.
At C:\Issue-PowershellThrowsErrorOnAppPoolStartMode.ps1:6 char:1
+ Set-ItemProperty IIS:\AppPools\delete.me startMode "AlwaysRunning" # throws an e ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Set-ItemProperty], Exception
    + FullyQualifiedErrorId : System.Exception,Microsoft.PowerShell.Commands.SetItemPropertyCommand

 

CPU’s resetLimit Can’t Directly Use New-TimeSpan’s Result

I think the example can show the problem better than I can describe it:

# https://connect.microsoft.com/PowerShell/feedbackdetail/view/1023785/webadministration-apppools-cpu-limit-interval-resetlimit-cant-be-set-directly
ipmo webadministration

New-WebAppPool "delete.me"

$a = Get-ItemProperty IIS:\AppPools\delete.me cpu
$a.resetInterval = New-TimeSpan -Minutes 4 # this will throw an error
Set-ItemProperty IIS:\AppPools\delete.me cpu $a

$a = Get-ItemProperty IIS:\AppPools\delete.me cpu
$k = New-TimeSpan -Minutes 4 # this will work
$a.resetInterval = $k
Set-ItemProperty IIS:\AppPools\delete.me cpu $a

Here is the error that gets thrown:

Set-ItemProperty : Specified cast is not valid.
At C:\Issue-PowershellThrowsErrorOnCpuLimitReset.ps1:8 char:1
+ Set-ItemProperty IIS:\AppPools\delete.me cpu $a
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Set-ItemProperty], InvalidCastException
    + FullyQualifiedErrorId : System.InvalidCastException,Microsoft.PowerShell.Commands.SetItemPropertyCommand

The links on each section correspond with bug reports for the issues, so hopefully they will get looked into.