Custom PowerShell cmdlet with a ScriptBlock in a hashtable

Question

I have a custom Powershell Cmdlet in C#, all works fine.

The one parameter is a HashTable. How can I use a ScriptBlock in that parameter? When I set the parameter to @{file={$_.Identity}}, I want to get a pipeline object with Identity property in the ProcessRecord method. How can I do that?

Now I simple convert the keys/values of the hash table to Dictionary<string, string>, but I want to get a pipelined object property (string).

Now I get an error that ScriptBlock can't convert to string.

Answer 1

You could use ForEach-Object for this:

function Invoke-WithUnderScore {
  param(
    [Parameter(ValueFromPipeline)]
    [object[]]$InputObject,
    [scriptblock]$Property
  )

  process {
    $InputObject |ForEach-Object $Property
  }
}

Then use like:

PS C:\> "Hello","World!","This is a longer string" |Invoke-WithUnderscore -Property {$_.Length}
5
6
23

---

Or in a C# cmdlet:

[Cmdlet(VerbsCommon.Select, "Stuff")]
public class SelectStuffCommand : PSCmdlet
{
    [Parameter(Mandatory = true, ValueFromPipeline = true)]
    public object[] InputObject;

    [Parameter()]
    public Hashtable Property;

    private List<string> _files;

    protected override void ProcessRecord()
    {
        string fileValue = string.Empty;
        foreach (var obj in InputObject)
        {
            if (!Property.ContainsKey("file"))
                continue;

            if (Property["file"] is ScriptBlock)
            {
                using (PowerShell ps = PowerShell.Create(InitialSessionState.CreateDefault2()))
                {
                    var result = ps.AddCommand("ForEach-Object").AddParameter("process", Property["file"]).Invoke(new[] { obj });
                    if (result.Count > 0)
                    {
                        fileValue = result[0].ToString();
                    }
                }
            }
            else
            {
                fileValue = Property["file"].ToString();
            }

            _files.Add(fileValue);
        }
    }

    protected override void EndProcessing()
    {
        // process _files
    }
}