Hosted PowerShell cannot see Cmdlets in the same Assembly

Question

I\'m trying to run PowerShell scripts from my C# code, that will use custom Cmdlets from the assembly that runs them. Here is the code:

Answer 1

You do need to register your cmdlet before you can use it in a Powershell session. You'll generally do that by way of a Powershell Snap-In. Here's a high-level overview of the process:

• Create custom cmdlets (you've already done this part)
• Create a Powershell Snap-in which contains and describes your cmdlets
• Install the new Snap-in on your system using Installutil
• Add the Snap-in to a specific Powershell session using Add-PSSnapin

There are a couple useful articles on MSDN that explain the process pretty thoroughly:

• Developing with Windows PowerShell
• How to Create a Windows PowerShell Snap-in

There's also a 2-part series on ByteBlocks that discusses writing custom cmdlets. That series may be your best bet, since you seem to have done the equivalent of part 1 already. You may be able to just use part 2 as a quick reference and be good to go.

• How to Write a Custom Cmdlet - Part 1
• How to Write a Custom Cmdlet - Part 2

Answer 2

The easiest way to do this with your current code snippet is like this:

using System; 
using System.Management.Automation; 

[Cmdlet(VerbsCommon.Get,"Hello")] 
public class GetHelloCommand:Cmdlet 
{ 
    protected override void EndProcessing() 
    { 
        WriteObject("Hello",true); 
    } 
} 

class MainClass 
{ 
    public static void Main(string[] args) 
    { 
        PowerShell powerShell=PowerShell.Create();

        // import commands from the current executing assembly
        powershell.AddCommand("Import-Module")
            .AddParameter("Assembly",
                  System.Reflection.Assembly.GetExecutingAssembly())
        powershell.Invoke()
        powershell.Commands.Clear()

        powershell.AddCommand("Get-Hello"); 
        foreach(string str in powerShell.AddCommand("Out-String").Invoke<string>()) 
            Console.WriteLine(str); 
    } 
} 

This assumes PowerShell v2.0 (you can check in your console with $psversiontable or by the copyright date which should be 2009.) If you're on win7, you are on v2.

Answer 3

Yet another simple way is to register cmdlets in a runspace configuration, create a runspace with this configuration, and use that runspace.

using System;
using System.Management.Automation;
using System.Management.Automation.Runspaces;

[Cmdlet(VerbsCommon.Get, "Hello")]
public class GetHelloCommand : Cmdlet
{
    protected override void EndProcessing()
    {
        WriteObject("Hello", true);
    }
}

class MainClass
{
    public static void Main(string[] args)
    {
        PowerShell powerShell = PowerShell.Create();
        var configuration = RunspaceConfiguration.Create();
        configuration.Cmdlets.Append(new CmdletConfigurationEntry[] { new CmdletConfigurationEntry("Get-Hello", typeof(GetHelloCommand), "") });
        powerShell.Runspace = RunspaceFactory.CreateRunspace(configuration);
        powerShell.Runspace.Open();

        powerShell.AddCommand("Get-Hello");
        foreach (string str in powerShell.AddCommand("Out-String").Invoke<string>())
            Console.WriteLine(str);
    }
}

Just in case, with this approach cmdlet classes do not have to be public.