SOLVED: Find web sites and applications using a Microsoft IIS server application pool using the WebAdministration PowerShell cmdlets

If you're using the older WebAdministration PowerShell module for IIS you'll notice when browing application pools you'll see the applications in the pool.

https://learn.microsoft.com/powershell/module/webadministration

However when you try and get the applications property it's not there because it's provided as a formatted property. You can grab the code from inside the formatter however there is a simpler method by enumerating the web sites and applications - these can be returned in the format

SiteName

or

SiteName\ApplicationName

# Gets the names of the applications in the specified application pool.
Function Get-ApplicationPoolApplicationNames
{
    [CmdletBinding()]
    param(

        [Parameter()]
        [System.Object] $ApplicationPoolName

    )
    process
    {
        $applicationNames = New-Object System.Collections.Generic.List``1[System.String];
        $webSites = Get-Website;
        foreach ($webSite in $webSites)
        {    
            if ($webSite.applicationPool -eq $ApplicationPoolName) { $applicationNames.Add($webSite.Name); }
            $applications = Get-WebApplication -Site $webSite.Name;
            foreach ($application in $applications)
            {
                if ($application.applicationPool -eq $ApplicationPoolName)
                {
                    $applicationNames.Add("$($webSite.Name)$($application.Path)");
                }
            }
        }
        return $applicationNames;
    }
}