Powershell . Declare generic list with class defined using 'Add-Type'

Question

I am trying to declare List in PowerShell, where the Person is defined using Add-Type:

add-type -Language CSharpVersion3 -TypeDefinition @"
    public class Person
    {
        public Person() {}

        public string First { get; set; }
        public string Last { get; set; }
    }
"@

This works fine:

New-Object Person
New-Object System.Collections.Generic.List``1[System.Object]

But this line fails:

New-Object System.Collections.Generic.List``1[Person]

What is wrong here?

For anyone else wondering, the line that fails (above) works in Powershell 3.0 (although i needed to remove "-Language CSharpVersion3" because I ran this on Windows Server 2012). — Steve Rathbone
– Steve Rathbone, Commented Jun 21, 2013 at 23:53

Michael Freidgeim · Accepted Answer · 2016-04-08 07:12:44Z

38

This is a bug in New-Object. This will help you create them more easily: http://www.leeholmes.com/blog/2006/08/18/creating-generic-types-in-powershell

UPDATE: PowerShell added support for this in Version 2:

PS > $r = New-Object "System.Collections.Generic.List[Int]"
PS > $r.Add(10)

edited Apr 8, 2016 at 7:12

Michael Freidgeim

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answered Mar 27, 2009 at 5:27

LeeHolmes

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1 Comment

Steven Murawski Over a year ago

Welcome to StackOverflow Lee!

Girardi · Accepted Answer · 2012-08-30 00:38:49Z

9

Well, I was trying to create a list of FileStream objects and this was my solution (based on this link -- which actually describes a way to solve your problem):

$fs = New-Object 'System.Collections.Generic.List[System.IO.FileStream]'
$sw = New-Object 'System.Collections.Generic.List[System.IO.StreamWriter]'
$i = 0
while ($i < 10)
{
    $fsTemp = New-Object System.IO.FileStream("$newFileName",[System.IO.FileMode]'OpenOrCreate',[System.IO.FileAccess]'Write')
    $fs.Add($fsTemp)
    $swTemp = New-Object System.IO.StreamWriter($fsTemp)
    $sw.Add($swTemp)
    $i++
}

Hope that helps!

answered Aug 30, 2012 at 0:38

Girardi

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