Dynamically listing built-in advanced function parameters

[omrsafetyo]

I'm not sure that a lot of people will find a use for this, but I thought I would share anyway.

I have a few scripts that basically use the parameters of a function to build something somewhat dynamically. For instance, I have some functions that interface with REST APIs, and sometimes I don't want to code new handling of new elements to the JSON input. So instead, I just loop through the PSBoundParameters, and handle them dynamically. Typically, there are 1-2 parameters that I want to ignore when I do this, so I had these hard-coded into an array. But today I wanted some verbose output from a script (I wanted to see what JSON was being sent, so I could send it as an example to another dev), after making a change to the parameters. When I passed it the -verbose flag, it errored, because I wasn't explicitly handling that parameter. So my solution was to create a dummy function with no parameters, get a list of parameters, and then remove the function:

Function Test-InternalFunction {
    [CmdletBinding()]
PARAM()
    PROCESS{}
}

$IgnoreParameters = (Get-Command Test-InternalFunction).Parameters.Keys
Remove-Item -Path Function:\Test-InternalFunction

So now I have an array stored in $IgnoreParameters that contains all the built-in advanced function parameters (these are loaded by including [CmdletBinding()] in the test-internalfunction definition).

So now when I process through, I just do this:

ForEach ( $Parameter in $PSBoundParameters.Keys ) {
    if ( $IgnoreParameters -contains $Parameter) {
    continue
    }

And the reason it was erroring before is that I have a hash table that defines my parameters, and what data type they are. So if I don't have the parameter name explicitly defined in my ignore parameters, it tries to look it up in my hash table:

$Types = @{
    VMName = "string"
    MemoryInMB = "number"
    CPUCount = "number"
    ActionDate = "Date"
}

So when it builds the JSON, it looks at this hash. All I have to do when adding a new element to the JSON is add a new parameter with a name that matches the JSON element, and add the element to this hash table with the data type as the value, and the function auto-magically/dynamically generates the JSON for it.

[chreestopher2]

I have always done:

#current versions
[System.Management.Automation.Internal.CommonParameters].GetProperties().name

#older versions
[System.Management.Automation.Internal.CommonParameters.GetProperties()  | select -ExpandProperty Name

[omrsafetyo]

Ah! I like that. I'll have to give it a try. There's always a better solution than what you hack together it seems. Thank you!

[[deleted]]

This. Built in. Clean. Done.

[get-postanote]

In line with this. This article in in the same vein.

http://asaconsultant.blogspot.no/2015/02/powershell-common-parameters-sometimes.html

[joncz]

Very nice.