Public/New-DynamicParam.ps1
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<# .SYNOPSIS Helper function to simplify creating dynamic parameters .DESCRIPTION Helper function to simplify creating dynamic parameters Example use cases: Include parameters only if your environment dictates it Include parameters depending on the value of a user-specified parameter Provide tab completion and intellisense for parameters, depending on the environment Please keep in mind that all dynamic parameters you create will not have corresponding variables created. One of the examples illustrates a generic method for populating appropriate variables from dynamic parameters Alternatively, manually reference $PSBoundParameters for the dynamic parameter value .NOTES Credit to http://jrich523.wordpress.com/2013/05/30/powershell-simple-way-to-add-dynamic-parameters-to-advanced-function/ Added logic to make option set optional Added logic to add RuntimeDefinedParameter to existing DPDictionary Added a little comment based help Credit to BM for alias and type parameters and their handling .PARAMETER Name Name of the dynamic parameter .PARAMETER Type Type for the dynamic parameter. Default is string .PARAMETER Alias If specified, one or more aliases to assign to the dynamic parameter .PARAMETER ValidateSet If specified, set the ValidateSet attribute of this dynamic parameter .PARAMETER Mandatory If specified, set the Mandatory attribute for this dynamic parameter .PARAMETER ParameterSetName If specified, set the ParameterSet attribute for this dynamic parameter .PARAMETER Position If specified, set the Position attribute for this dynamic parameter .PARAMETER ValueFromPipelineByPropertyName If specified, set the ValueFromPipelineByPropertyName attribute for this dynamic parameter .PARAMETER HelpMessage If specified, set the HelpMessage for this dynamic parameter .PARAMETER DPDictionary If specified, add resulting RuntimeDefinedParameter to an existing RuntimeDefinedParameterDictionary (appropriate for multiple dynamic parameters) If not specified, create and return a RuntimeDefinedParameterDictionary (appropriate for a single dynamic parameter) See final example for illustration .EXAMPLE function Show-Free { [CmdletBinding()] Param() DynamicParam { $options = @( gwmi win32_volume | %{$_.driveletter} | sort ) New-DynamicParam -Name Drive -ValidateSet $options -Position 0 -Mandatory } BEGIN { #have to manually populate $drive = $PSBoundParameters.drive } PROCESS { $vol = gwmi win32_volume -Filter "driveletter='$drive'" "{0:N2}% free on {1}" -f ($vol.Capacity / $vol.FreeSpace),$drive } } #Show-Free Show-Free -Drive <tab> This example illustrates the use of New-DynamicParam to create a single dynamic parameter The Drive parameter ValidateSet populates with all available volumes on the computer for handy tab completion / intellisense .EXAMPLE I found many cases where I needed to add more than one dynamic parameter The DPDictionary parameter lets you specify an existing dictionary The block of code in the Begin block loops through bound parameters and defines variables if they don't exist Function Test-DynPar{ [cmdletbinding()] param( [string[]]$x = $Null ) DynamicParam { #Create the RuntimeDefinedParameterDictionary $Dictionary = New-Object System.Management.Automation.RuntimeDefinedParameterDictionary New-DynamicParam -Name AlwaysParam -ValidateSet @( gwmi win32_volume | %{$_.driveletter} | sort ) -DPDictionary $Dictionary #Add dynamic parameters to $dictionary if ($x -eq 1) { New-DynamicParam -Name X1Param1 -ValidateSet 1,2 -mandatory -DPDictionary $Dictionary New-DynamicParam -Name X1Param2 -DPDictionary $Dictionary New-DynamicParam -Name X3Param3 -DPDictionary $Dictionary -Type DateTime } else { New-DynamicParam -Name OtherParam1 -Mandatory -DPDictionary $Dictionary New-DynamicParam -Name OtherParam2 -DPDictionary $Dictionary New-DynamicParam -Name OtherParam3 -DPDictionary $Dictionary -Type DateTime } #return RuntimeDefinedParameterDictionary $Dictionary } BEGIN { #This standard block of code loops through bound parameters... #If no corresponding variable exists, one is created #Get common parameters, pick out bound parameters not in that set Function _temp { [cmdletbinding()] param() } $BoundKeys = $PSBoundParameters.keys | Where-Object { (get-command _temp | select -ExpandProperty parameters).Keys -notcontains $_} foreach($param in $BoundKeys) { if (-not ( Get-Variable -name $param -scope 0 -ErrorAction SilentlyContinue ) ) { New-Variable -Name $Param -Value $PSBoundParameters.$param Write-Verbose "Adding variable for dynamic parameter '$param' with value '$($PSBoundParameters.$param)'" } } #Appropriate variables should now be defined and accessible Get-Variable -scope 0 } } This example illustrates the creation of many dynamic parameters using New-DynamicParam You must create a RuntimeDefinedParameterDictionary object ($dictionary here) To each New-DynamicParam call, add the -DPDictionary parameter pointing to this RuntimeDefinedParameterDictionary At the end of the DynamicParam block, return the RuntimeDefinedParameterDictionary Initialize all bound parameters using the provided block or similar code .FUNCTIONALITY PowerShell Language #> function New-DynamicParam { [CmdletBinding(SupportsShouldProcess)] param( [string] $Name, [System.Type] $Type = [string], [string[]] $Alias = @(), [string[]] $ValidateSet, [switch] $Mandatory, [string] $ParameterSetName="__AllParameterSets", [int] $Position, [switch] $ValueFromPipelineByPropertyName, [string] $HelpMessage, [validatescript( { if (-not ( $_ -is [System.Management.Automation.RuntimeDefinedParameterDictionary] -or -not $_) ) { throw "DPDictionary must be a System.Management.Automation.RuntimeDefinedParameterDictionary object, or not exist" } $True } )] $DPDictionary = $false ) PROCESS { if($PSCmdlet.ShouldProcess()){ #Create attribute object, add attributes, add to collection $ParamAttr = New-Object System.Management.Automation.ParameterAttribute $ParamAttr.ParameterSetName = $ParameterSetName if ($mandatory) { $ParamAttr.Mandatory = $True } if ($Position -ne $null) { $ParamAttr.Position=$Position } if ($ValueFromPipelineByPropertyName) { $ParamAttr.ValueFromPipelineByPropertyName = $True } if ($HelpMessage) { $ParamAttr.HelpMessage = $HelpMessage } $AttributeCollection = New-Object 'Collections.ObjectModel.Collection[System.Attribute]' $AttributeCollection.Add($ParamAttr) #param validation set if specified if($ValidateSet) { $ParamOptions = New-Object System.Management.Automation.ValidateSetAttribute -ArgumentList $ValidateSet $AttributeCollection.Add($ParamOptions) } #Aliases if specified if ($Alias.count -gt 0) { $ParamAlias = New-Object System.Management.Automation.AliasAttribute -ArgumentList $Alias $AttributeCollection.Add($ParamAlias) } #Create the dynamic parameter $Parameter = New-Object -TypeName System.Management.Automation.RuntimeDefinedParameter -ArgumentList @($Name, $Type, $AttributeCollection) #Add the dynamic parameter to an existing dynamic parameter dictionary, or create the dictionary and add it if ($DPDictionary) { $DPDictionary.Add($Name, $Parameter) } else { $Dictionary = New-Object System.Management.Automation.RuntimeDefinedParameterDictionary $Dictionary.Add($Name, $Parameter) $Dictionary } } } } |