PowerShell: retrieve number of applications in AppPool

The trick is: PowerShell established so-called "view definition files" which tell PowerShell how to format objects (e.g. whether the object is formatted as a a list or a table, which columns are displayed, etc.). Those files can be found at C:\Windows\System32\WindowsPowerShell\v1.0 and are all ending in .format.ps1xml.

To answer the original question: The file C:\Windows\System32\WindowsPowerShell\v1.0\Modules\WebAdministration\iisprovider.format.ps1xml contains the view definition for the AppPool type which defines a calculated column looking like this:

<TableColumnItem> <ScriptBlock>    $pn = $_.Name    $sites = get-webconfigurationproperty "/system.applicationHost/sites/site/application[@applicationPool=`'$pn`'and @path='/']/parent::*" machine/webroot/apphost -name name    $apps = get-webconfigurationproperty "/system.applicationHost/sites/site/application[@applicationPool=`'$pn`'and @path!='/']" machine/webroot/apphost -name path    $arr = @()    if ($sites -ne $null) {$arr += $sites}    if ($apps -ne $null) {$arr += $apps}    if ($arr.Length -gt 0) {      $out = ""      foreach ($s in $arr) {$out += $s.Value + "`n"}      $out.Substring(0, $out.Length - 1)    }  </ScriptBlock></TableColumnItem>

This answers why the column itself is not a member of the AppPool type. The second question can be easily answered now extracting the necessary code from the "scriptlet" above:

$applicationsInAppPoolCount = @(Get-WebConfigurationProperty `"/system.applicationHost/sites/site/application[@applicationPool=`'$appPool`'and @path!='/']"` "machine/webroot/apphost" -name path).Count

I dealt with this same issue for many hours until finally arriving at the solution. The answer from D.R. was very helpful but it was not working for me. After some tweaks, I came up with the code below which retrieves the number of applications in an app pool.

I noticed that this part of the code nd @path!='/' threw off the count.

$appPool = "REPLACE ME with a value from your app pool"@(Get-WebConfigurationProperty "/system.applicationHost/sites/site/application[@applicationPool=`'$appPool`']" "machine/webroot/apphost" -name path).Count

I ended up with the following Code (basically the same as above, but differently formatted)

$appPools = Get-ChildItem –Path IIS:\AppPoolsforeach ($apppool in $apppools) {  $appoolName = $apppool.Name  [string] $NumberOfApplications = (Get-WebConfigurationProperty "/system.applicationHost/sites/site/application[@applicationPool='$appoolName']" "machine/webroot/apphost" -name path).Count  Write-Output "AppPool name: $appoolName has $NumberOfApplications applications"}