As you might know, you can add attributes to variables and parameters to more specifically define them. For example, the line below defines a function with a parameter that accepts only three distinct string values and is mandatory:
function Test-Attribute { [CmdletBinding()] param ( [string] [Parameter(Mandatory)] [ValidateSet("A","B","C")] $Choice ) "Choice: $Choice" }
If you ever wondered what your choices are with these attributes, here is how. All you need to know is the true name of the type that represents an attribute. PowerShell’s own attributes all reside in the System.Management.Automation namespace. Here are the two most commonly used:
[Parameter()] = [System.Management.Automation.ParameterAttribute]
[CmdletBinding()] = [System.Management.Automation.CmdletBindingAttribute]
To find out the legal values for a given attribute, simply instantiate an object of the given type, and look at its properties:
[System.Management.Automation.ParameterAttribute]::new() | Get-Member -MemberType *Property | Select-Object -ExpandProperty Name
This yields the list of legal attribute values for the [Parameter()] attribute:
DontShow HelpMessage HelpMessageBaseName HelpMessageResourceId Mandatory ParameterSetName Position TypeId ValueFromPipeline ValueFromPipelineByPropertyName ValueFromRemainingArguments
When you add the expected data type to each value, the list becomes even more usable:
[System.Management.Automation.ParameterAttribute]::new() | Get-Member -MemberType *Property | ForEach-Object { [PSCustomObject]@{ Name = $_.Name Type = ($_.Definition -split ' ')[0] } }
Now it looks similar to this:
Name Type ---- ---- DontShow bool HelpMessage string HelpMessageBaseName string HelpMessageResourceId string Mandatory bool ParameterSetName string Position int TypeId System.Object ValueFromPipeline bool ValueFromPipelineByPropertyName bool ValueFromRemainingArguments bool
And this would be the list for [CmdletBinding()]:
[System.Management.Automation.CmdletBindingAttribute]::new() | Get-Member -MemberType *Property | ForEach-Object { [PSCustomObject]@{ Name = $_.Name Type = ($_.Definition -split ' ')[0] } }
Name Type ---- ---- ConfirmImpact System.Management.Automation.ConfirmImpact DefaultParameterSetName string HelpUri string PositionalBinding bool RemotingCapability System.Management.Automation.RemotingCapability SupportsPaging bool SupportsShouldProcess bool SupportsTransactions bool TypeId System.Object
