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
 

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