Access common powershell cmdlet parameters from c#

Question

more specific I want to access the value of the ErrorAction parameter from withing the cmdlet.

In powershell everything works as expected

function Get-Test {
    [CmdletBinding()]
    param (

    )
    (Get-Variable|where{$_.Name -eq "ErrorActionPreference"}).Value

}
Get-Test -ErrorAction SilentlyContinue

will output SilentContinue

However the same call in c# will output Continue

    [CmdletBinding]
    [Cmdlet(VerbsCommon.Get,"Test")]
    public class MyClass:PSCmdlet{
        protected override void ProcessRecord(){
            base.ProcessRecord();
            WriteObject(((PSVariable) InvokeCommand.InvokeScript($"Get-Variable|where{{$_.Name -eq 'ErrorActionPreference'}}").First().BaseObject).Value);
        }
    }

it looks like there is no link between the ErrorAction parameter and the ErrorActionPreference when c#. I say this because if I do

$ErrorActionPreference="SilentlyContinue"
Get-Test # c# version

will output SilentlyContinue

mklement0 · Accepted Answer · 2019-03-04 02:09:33Z

Generally, from within (by definition compiled) cmdlets there is no need to determine whether a common parameter was passed or whether its value is implied by a previously set preference variable:

Cmdlets can rely on the infrastructure provided by their base class to automatically act appropriately on any common-parameter values passed explicitly or implied by preference variables.
- E.g., a WriteVerbose() call implicitly adjusts its output behavior based on whether -Verbose was explicitly specified on cmdlet invocation and, in its absence, the value of the $VerbosePreference preference variable in the caller's scope.

In advanced functions - the implemented-in-PowerShell counterparts to compiled cmdlets - explicitly specified common parameters are automaticaly translated into function-scoped preference variables.

This is an implementation detail, however, and, regrettably, one that is highly problematic.
However, when it does work as intended - in advanced functions originating in the same scope domain as the caller - the effect is the same as in compiled cmdlets: Calls to cmdlets such as Write-Verbose do implicitly pick up both explicitly specified common parameters as well as the caller's preference-variable values (in the latter case via scopes in the same scope domain implicitly seeing variables in the (nearest) ancestral scope).

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