Type-Based Parameter Binding (Part 2)

PowerShell 2+

In a previous tip we introduced automatic type-based parameter binding. Here is a use case. The function Test-Binding accepts files and folders. For incoming files, it calculates the file size. For incoming folders, it emits a warning. Note how the parameter binding works per incoming element:

function Test-Binding
{
  #Content
  param
  (
    [System.IO.FileInfo]
    [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='File', Position=0)]
    $File,
  
    [System.IO.DirectoryInfo]
    [Parameter(Mandatory,ValueFromPipeline,ParameterSetName='Folder',Position=0 )]
    $Folder,
    
    [Parameter(ParameterSetName='File', ValueFromPipelineByPropertyName)]
    $Length
  )
  
  process
  {
  
    if ($PSCmdlet.ParameterSetName -eq 'File')
    {
      'File Size: {0:n1} MB' -f ($Length/1MB)
    }
    else
    {
      Write-Warning "Folder ignored: $Folder"
    }
  }
}


Get-ChildItem c:\windows | Test-Binding -Verbose

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