I am trying to use the CompressEx method of the Win32_Directory class to compress the %systemroot%\system32\LogFiles directory during a server build process. The code I am currently using is

(Get-WmiObject -class "Win32_Directory" -filter "name='$systemroot\\System32\\LogFiles'" -ErrorVariable errorstatus -ErrorAction SilentlyContinue).CompressEx("",$true)

This works great for compressing a folder and its subfolders and files. However, the problem with this method is that when it hits an error, a sharing violation in my case, it stops the process and stores the file on which it errored in .StopFileName. The method does not appear to have any kind of "SilentlyContinue" type functionality to it. From what I gathered on this method, you should be able to take the .StopFileName value and plug it back in as the StartFileName (shown as "" in my example above) and run it again. But this doesn't work either as it just fails on the same file again. Seems like you really need .StopFileName + 1 in the array of folders/files it builds but of course you can't touch that array.

I suppose as a workaround, I can build by own array of subfolders under \LogFiles and step through using the .Compress method instead which would just compress the folder and thus any new files created under those folders which is my intent really. But I'd like to know how to error handle .CompressEx. Anyone familiar with this method?

That's a really interesting problem. I might actually approach this be possibly querying WMI and/or .NET experts on this. I do believe you are going to be out of luck on this one. Even if PowerShell can be set to handle the error, it will not continue to move on to the next file, it will want to basically move to the next command... Regardless of it being one of the 2 major types of errors: terminating or non-terminating.

Yeah, it's obviously more of a WMI thing, kind of seems like a flaw in the .Compress and .CompressEx methods. I just worked around the issue using the following code instead

$systemroot = $env:systemroot
$path = "$systemroot\system32\LogFiles" -replace '\\','\\'

(Get-WmiObject -class "Win32_Directory" -filter "name='$path'" -ErrorVariable errorstatus -ErrorAction SilentlyContinue).Compress()

foreach($folder in Get-ChildItem $path | where {$_.psIsContainer -eq $true}) {
$a = $folder.fullname -replace '\\','\\'
(Get-WmiObject -class "Win32_Directory" -filter "name='$a'" -ErrorVariable errorstatus -ErrorAction SilentlyContinue).Compress()
}

It still hits the sharing violation when it compresses the subfolder that contains the in-use file(s) as .Compress also attempts to compress any files under the subfolder. But since the folder is marked as compressed first, it achieves my desired result in that any new logs created when rolling over are created as compressed. A real kludge and not desirable if I was doing this on existing servers where \LogFiles might already contain existing files but fits my immediate needs.