calling Invoke-Expression with Parameters in Powershell
I know this is a little old now, but I was having a similar issue and a co-worker showed me that escaping $argstr prevents the object from getting converted to a string.
Invoke-Expression "Add-VM `$argstr"
That error is from Invoke-Expression not Add-VM and you just need quotes around the argument:
Invoke-Expression "Add-VM $argstr"This has the drawback of forcing all objects into string format. This might be acceptable for simple types like ints and strings but if you want to pass through a more complex object it won't work. An alternative would be to splat the arguments with @args but I don't think you can do this through Invoke-Expression or Invoke-Command. You need to directly call the cmdlet:
function newtask { params([string]$command) switch ($command) { "addvm" { Add-VM @args } "deletevm" { Remove-VM @args } }}