Powershell: Openfile dialog and Set-Content Issue. Cannot access file. In use - powershell

Question

What I'm trying to do is utilize the openfile dialog, select an ini file and make line changes to it at the end of this script with set-content. But I keep getting the error that Set-Content : The process cannot access the file, and that it's in use.
$a = $env:userprofile
Function Get-FileName($InitialDirectory)
{
Get-FileName -InitialDirectory "$a\AppData\Roaming\Milliman"
}#end function Get-FileName
[System.Reflection.Assembly]::LoadWithPartialName("System.windows.forms") | Out-Null
$dialog = New-Object System.Windows.Forms.OpenFileDialog
$dialog.DefaultExt = '.*'
$dialog.Filter = 'All Files|*.*'
$dialog.FilterIndex = 0
$dialog.InitialDirectory = $InitialDirectory
$dialog.Multiselect = $false
$dialog.RestoreDirectory = $true
$dialog.Title = "Select a file"
$dialog.ValidateNames = $true
$dialog.ShowHelp = $true
$dialog.ShowDialog()
$dialog.FileName
##Folder Dialog
$dir = new-object -com Shell.Application
$aldir = $dir.BrowseForFolder(0, "AL Dir", 0, "C:\Program Files\Milliman\")
if ($aldir.Self.Path -ne "") {write-host "You selected " $aldir.Self.Path}
## Grid Integration Steps
Copy-Item -path "\\ap102aric\alfaadmin$\Ver70andAbove\DataSynapse\*" -destination "C:\Program Files\Common Files\Milliman\MG-ALFA Shared\DataSynapse" -Force
Copy-Item -path "\\ap102aric\alfaadmin$\Ver70andAbove\JobOptions-RPRic\*" -destination "C:\Program Files\Common Files\Milliman\MG-ALFA Shared\DataSynapse" -Force
Copy-Item -path "\\ap102aric\alfaadmin$\Ver70andAbove\GSDLL\dsdrv.dll" -Destination $aldir.Self.Path -Force
## Set Environment Variable
[Environment]::SetEnvironmentVariable("DSDRIVER_DIR","C:\Program Files\Common Files\Milliman\MG-ALFA Shared\DataSynapse\Config","Machine")
## Edit Config UI.ini to set SDP LOGON for Datasynapse
#Write-Host $dialog.FileName
Get-Content $dialog.FileName | ForEach-Object {
$_ -replace 'SDPAvailable=*','SDPAvailable=DataSynapse'
-replace 'SDPFolder=*','SDPFolder=C:\Program Files\Common Files\Milliman\MG-ALFA Shared\DataSynapse'
-replace 'SDPLogon=*','SDPAvailable=Yes'
} | Set-Content $dialog.FileName

Answer 1

Try destroying the $aldir object. It may be holding a handle to the file. I'm not sure how to do that. Maybe set it to $null after you grab the path the user selected.
You can also try using Process Monitor to figure out what process is locking the file.
Finally, you can't pipe the output from Get-Content to Set-Content, e.g.
Get-Content $Path | Set-Content $Path
Items are sent down the PowerShell pipeline immediately, so when Get-Content reads a line, it immediately gets set to Set-Content, which won't work because Get-Content has the file open. Instead, try saving the contents of the file:
$file = Get-Content $path
# Modify $file
$file | Set-Content $path