How to safely read from / write to text files using .NET in PowerShell

FileAccessNETDemo.ps1

$outputFilePath = "drive:\path\to\file.txt" # will work with files on remote file servers (-> UNC paths), too

try {
    if (Test-Path -Path $outputFilePath -PathType Leaf) {
        try {
            $fStream = [System.IO.FileStream]::New($outputFilePath, [System.IO.FileMode]::Open, [System.IO.FileAccess]::ReadWrite, [System.IO.FileShare]::None) # exclusively open file for read/write
        } catch [System.IO.IOException] {
            throw [System.Management.Automation.RuntimeException]::New("The file '" + $outputFilePath + "' could not be opened - aborted!", $_.Exception)
        }
    } else {
        try {
            $fStream = [System.IO.File]::Create($outputFilePath) # create new file
        } catch {
            throw [System.Management.Automation.RuntimeException]::New("The file '" + $outputFilePath + "' could not be created - aborted!", $_.Exception)
        }
    }

    if ($fStream.CanWrite) { # checking for write access also includes read access, so there's no need to check both
        $enc = [System.Text.Utf8Encoding]::New() # let's assume the file content is encoded in UTF-8

        # just an example of how to read data from the file, using the FileStream object we instantiated above
        if ($fStream.Length -gt 0) {
            $sBytes = [Byte[]]::New($fStream.Length)
            [Int]$bRead = 0

            do {
                $fStream.Read($sBytes, $bRead, $fStream.Length) | Out-Null
            } while ($bRead -gt 0)

            [String]$dataStr = $enc.GetString($sBytes).Trim() 2>$null

            # ... do something with the read data ...
            Write-Host $("File data: `r`n" + $dataStr)
        }

        # Write something to the file; in this demo, it's a timestamp
        $curDate = Get-Date
        $dateStr = $(if ($fStream.Length -gt 0) { "`r`n" } else { "" }) + $curDate.Ticks.ToString() + " (" + ("{0:dd.MM.yyyy}" -f $curDate) + ")"
        $fStream.Seek(0, [System.IO.SeekOrigin]::End) | Out-Null # add the content to the end of the file
        $fStream.Write($enc.GetBytes($dateStr), 0, $enc.GetByteCount($dateStr))
    } else {
        throw [System.Management.Automation.RuntimeException]::New("The file '" + $outputFilePath + "' could not be modified - aborted!")
    }
} finally {
    if ($fStream) {
        # cleanup
        try {
            $fStream.Close()
            $fStream = $null
        } catch {
            # ignore errors
        }
    }
}