I am trying to dispose XmlWriter object:
try
{
[System.Xml.XmlWriter] $writer = [System.Xml.XmlWriter]::Create('c:\some.xml')
}
finally
{
$writer.Dispose()
}
Error:
Method invocation failed because [System.Xml.XmlWellFormedWriter] doesn't contain a method named 'Dispose'.
On the other side:
$writer -is [IDisposable]
# True
What should I do?
Dispose is protected on System.Xml.XmlWriter. You should use Close instead.
$writer.Close
Dispose. The Dispose he wants is not protected; it is an explicit interface implementation! Explicit interface implementations are hard to call from PowerShell. But this hack should work: [IDisposable].GetMethod("Dispose").Invoke($writer, @()).Here is an alternative approach:
(get-interface $obj ([IDisposable])).Dispose()
Get-Interface script can be found here http://www.nivot.org/2009/03/28/PowerShell20CTP3ModulesInPracticeClosures.aspx and was suggested in this response.
With 'using' keyword we get:
$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')) {
}
