Clear-Host
$ErrorActionPreference = [System.Management.Automation.ActionPreference]::Stop


$fileSystemWatcherDirPath = 'C:\temp'
$fileSystemWatcherFilter = '*.*'

$fileSystemWatcher = [System.IO.FileSystemWatcher]::new($fileSystemWatcherDirPath , $fileSystemWatcherFilter)
$fileSystemWatcher.IncludeSubdirectories = $true
$fileSystemWatcher.EnableRaisingEvents = $true
$fileSystemWatcher.NotifyFilter = [System.IO.NotifyFilters]::FileName -bor [System.IO.NotifyFilters]::DirectoryName -bor [System.IO.NotifyFilters]::LastWrite  # [System.Linq.Enumerable]::Sum([System.IO.NotifyFilters].GetEnumValues())

# Create syncronized hashtable
$syncdFsItemEventHashT = [hashtable]::Synchronized([hashtable]::new())

$fileSystemWatcherAction = {
    try {
        $fsItemEvent = [pscustomobject]@{
            EventIdentifier  = $Event.EventIdentifier
            SourceIdentifier = $Event.SourceIdentifier
            TimeStamp        = $Event.TimeGenerated
            FullPath         = $Event.SourceEventArgs.FullPath
            ChangeType       = $Event.SourceEventArgs.ChangeType
        }

        # Collecting event in synchronized hashtable (overrides existing keys so that only the latest event details are available)
        $syncdFsItemEventHashT[$fsItemEvent.FullPath] = $fsItemEvent
    } catch {
        Write-Host ($_ | Format-List * | Out-String ) -ForegroundColor red
    }
}


# Script block which processes collected events and do further actions like copying for backup, etc...
# That scriptblock was initially used to test "Start-Job". Unfortunately it's not possible to access and modify the synchronized hashtable created within this scope.
$fSItemEventProcessingJob = {
    $keys = $syncdFsItemEventHashT.psbase.Keys

    foreach ($key in $keys) {
        $fsEvent = $syncdFsItemEventHashT[$key]

        try {
            if ($fsEvent.ChangeType -eq [System.IO.WatcherChangeTypes]::Deleted) {
                $syncdFsItemEventHashT.Remove($key )
                Write-Host ("==> Item '$key' with changetype '$($fsEvent.ChangeType)' removed from hashtable without any further actions!") -ForegroundColor Blue
                continue
            }

            # get filesystem object
            $fsItem = Get-Item -LiteralPath $fsEvent.FullPath

            if ($fsItem -is [System.IO.FileInfo]) {
                # file processing

                try {
                    # Check whether the file is still locked / in use by another process
                    [System.IO.FileStream]$fileStream = [System.IO.File]::Open( $fsEvent.FullPath, [System.IO.FileMode]::Open, [System.IO.FileAccess]::Read, [System.IO.FileShare]::Read)
                    $fileStream.Close()
                } catch [System.IO.IOException] {
                    Write-Host ("==> Item '$key' with changetype '$($fsEvent.ChangeType)' is still in use and can't be read!") -ForegroundColor Yellow
                    continue
                }
            }elseIf($fsItem -is [System.IO.DirectoryInfo]) {
                # directory processing
            }

            $syncdFsItemEventHashT.Remove($key )
            Write-Host ("==> Item '$key' with changetype '$($fsEvent.ChangeType)' has been processed and removed from hashtable.") -ForegroundColor Blue

        } catch {
            Write-Host ($_ | Format-List * | Out-String ) -ForegroundColor red
        }
    }
}

[void] (Register-ObjectEvent -InputObject $fileSystemWatcher -EventName 'Created' -SourceIdentifier 'FSCreated' -Action $fileSystemWatcherAction)
[void] (Register-ObjectEvent -InputObject $fileSystemWatcher -EventName 'Changed' -SourceIdentifier 'FSChanged' -Action $fileSystemWatcherAction)
[void] (Register-ObjectEvent -InputObject $fileSystemWatcher -EventName 'Renamed' -SourceIdentifier 'FSRenamed' -Action $fileSystemWatcherAction)
[void] (Register-ObjectEvent -InputObject $fileSystemWatcher -EventName 'Deleted' -SourceIdentifier 'FSDeleted' -Action $fileSystemWatcherAction)



Write-Host "Watching for changes in '$fileSystemWatcherDirPath'.`r`nPress CTRL+C to exit!"
try {
    do {
        Wait-Event -Timeout 1

        if ($syncdFsItemEventHashT.Count -gt 0) {
            Write-Host "`r`n"
            Write-Host ('-' * 50) -ForegroundColor Green
            Write-Host "Collected events in hashtable queue:" -ForegroundColor Green
            $syncdFsItemEventHashT.Values | Format-Table | Out-String
        }

        # Process hashtable items and do something with them (like copying, ..)
        .$fSItemEventProcessingJob

    } while ($true)

} finally {
    # unregister
    Unregister-Event -SourceIdentifier 'FSChanged'
    Unregister-Event -SourceIdentifier 'FSCreated'
    Unregister-Event -SourceIdentifier 'FSDeleted'
    Unregister-Event -SourceIdentifier 'FSRenamed'

    # dispose
    $FileSystemWatcher.EnableRaisingEvents = $false
    $FileSystemWatcher.Dispose()
    Write-Host "`r`nEvent Handler removed."
}