Getting all Named Parameters from Powershell including empty and set ones

Question

Check this solution out. This uses the CmdletBinding() attribute, which provides some additional metadata through the use of the $PSCmdlet built-in variable. You can:

1. Dynamically retrieve the command's name, using $PSCmdlet
2. Get a list of the parameter for the command, using Get-Command
3. Examine the value of each parameter, using the Get-Variable cmdlet

Code:

function test {
    [CmdletBinding()]
    param (
          [string] $Bar = 'test'
        , [string] $Baz
        , [string] $Asdf
    )
    # Get the command name
    $CommandName = $PSCmdlet.MyInvocation.InvocationName;
    # Get the list of parameters for the command
    $ParameterList = (Get-Command -Name $CommandName).Parameters;

    # Grab each parameter value, using Get-Variable
    foreach ($Parameter in $ParameterList) {
        Get-Variable -Name $Parameter.Values.Name -ErrorAction SilentlyContinue;
        #Get-Variable -Name $ParameterList;
    }
}

test -asdf blah;

Output

The output from the command looks like this:

Name                           Value                                           
----                           -----                                           
Bar                            test                                            
Baz                                                                            
Asdf                           blah                                            

To read the value dynamically use the get-variable function / cmdlet

write-host (get-variable "foo")

To print out all of the parameters do the following

foreach ($key in $MyInvocation.BoundParameters.keys)
{
    $value = (get-variable $key).Value 
    write-host "$key -> $value"
}

I found this most useful for PS4 (Windows 2012 R2) - it includes default values / optional parameters:

$cmdName = $MyInvocation.InvocationName
$paramList = (Get-Command -Name $cmdName).Parameters
foreach ( $key in $paramList.Keys ) {
    $value = (Get-Variable $key -ErrorAction SilentlyContinue).Value
    if ( $value -or $value -eq 0 ) {
        Write-Host "$key -> $value"
    }
}

Hopefully, some may find this one-liner useful:

function test()
{
    Param(
        [string]$foo,
        [string]$bar,
        [string]$baz = "baz"
    )

    $MyInvocation.MyCommand.Parameters | Format-Table -AutoSize @{ Label = "Key"; Expression={$_.Key}; }, @{ Label = "Value"; Expression={(Get-Variable -Name $_.Key -EA SilentlyContinue).Value}; }
}
test -foo "foo!"

Result

Keys Value
---- -----
foo  foo! 
bar       
baz  baz