Come posso smaltire System.Xml.XmlWriter in PowerShell

Question

Sto cercando di smaltire oggetto XmlWriter:

try 
{ 
    [System.Xml.XmlWriter] $writer = [System.Xml.XmlWriter]::Create('c:\some.xml') 
} 
finally 
{ 
    $writer.Dispose() 
} 

Errore:

Method invocation failed because [System.Xml.XmlWellFormedWriter] doesn't contain a method named 'Dispose'.

Dall'altra parte:

$writer -is [IDisposable] 
# True 

Cosa dovrei fare?

Answer 1

Dispose è protected su System.Xml.XmlWriter. Dovresti usare invece Close.

$writer.Close 

Answer 2

Ecco un approccio alternativo:

(get-interface $obj ([IDisposable])).Dispose() 

script Get-Interface può essere trovato qui http://www.nivot.org/2009/03/28/PowerShell20CTP3ModulesInPracticeClosures.aspx ed è stato suggerito in questo response.

Con 'usando' parola chiave otteniamo:

$MY_DIR = Split-Path -Path $MyInvocation.MyCommand.Definition -Parent 

# http://www.nivot.org/2009/03/28/PowerShell20CTP3ModulesInPracticeClosures.aspx 
. ($MY_DIR + '\get-interface.ps1') 

# A bit modified code from http://blogs.msdn.com/powershell/archive/2009/03/12/reserving-keywords.aspx 
function using 
{ 
    param($obj, [scriptblock]$sb) 

    try { 
     & $sb 
    } finally { 
     if ($obj -is [IDisposable]) { 
      (get-interface $obj ([IDisposable])).Dispose() 
     } 
    } 
} 

# Demo 
using($writer = [System.Xml.XmlWriter]::Create('c:\some.xml')) { 

}