How to write and import Cmdlet inside Powershell script with C#

Question

I want to write cmdlet in c# just inside powershell script, so that I don't need to compile it myself, and also can leverage the WriteObject()/WriteError() functions, but it doesn't work, anyone know how to do this?

$code = @"
    using System;
    using System.Management.Automation;

    [Cmdlet("Write", "Hello")]
    public class WriteHello : PSCmdlet
    {
        [Parameter(Position =0)]
        public  String Msg  { get; set; }

        protected override void ProcessRecord()
        {
            //WriteObject("Hello: " + Msg);
            Console.WriteLine("Hello: " + Msg);
        }
    }
"@

    Add-Type $code

    $cmdlet = [WriteHello]::new()
    # Error when invoke().
    $cmdlet.Invoke()

7cc · Accepted Answer · 2020-06-16 06:37:34Z

1

First, please share errors messages:

An error occurred while enumerating through a collection: Cmdlets derived from PSCmdlet cannot be invoked directly.

It's obvious.

Solution 1

Use Cmdlet instead of PSCmdlet if that satisfies your needs.

Solution 2

$code = ...
Add-Type $code
$WriteHello = [System.Management.Automation.CmdletInfo]::new("Write-Hello", [WriteHello])
& $WriteHello -msg "abcd"

I recommend to compile the source code anyway. Add-Type is basically a wrapper of pre-installed "cscript.exe". It create a CS file in the Temp directory and compile it.

Edit

Import-Module from a source code.

Add-Type $code -PassThru | % { Import-Module $_.Assembly }

edited Jun 16, 2020 at 6:37

answered Jun 15, 2020 at 5:48

7cc

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2 Comments

xinglong Over a year ago

Great, thanks, I use Add-Type to compile it to avoid manually compile after each time I modified it. Do you know if it is possible to register the Write-Hello cmdlet, so that I can directly invoke it by: Write-Hello -msg abcd

7cc Over a year ago

@xinglong I updated the answer. Please try after Edit.

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