Transfer files over FTP/HTTP with piping support using Powershell

PSTransfer.ps1

<#
.SYNOPSIS
    Transfers files over HTTP or FTP.
.DESCRIPTION
    Downloads or uploads files over HTTP or FTP. Supports user authentication and piped file names.
.PARAMETER UserName
    The user account name or an anonymous connection if missing.
.PARAMETER Password
    The user account password.
.PARAMETER FileName
    The file to transfer. This parameter is used when piping to PSTransfer.
.PARAMETER ServerPath
    The remote server directory path.
.PARAMETER LocalPath
    The local file directory path or the local directory if missing.
.PARAMETER Action
    The transfer to perform, Upload or Download.
.EXAMPLE
    .\PSTransfer.ps1 -FileName file.zip -ServerPath ftp://ftp.example.com -Action Download
    Downloads file.zip from ftp.example.com into the current folder using an anonymous login.
.EXAMPLE
    type files.txt | % { .\PSTransfer.ps1 -UserName john -Password doe -FileName $_ -ServerPath ftp://example.com/ -LocalPath . -Action Download }
    Downloads all files listed in files.txt.
#>

param(
    [string]$UserName = "anonymous",
    [string]$Password = "anonymous@example.com",
    [Parameter(Mandatory=$True, ValueFromPipeline=$True)]
    [string]$FileName,
    [Parameter(Mandatory=$True)]
    [string]$ServerPath,
    [string]$LocalPath = ".",
    [Parameter(Mandatory=$True)]
    [ValidateSet("Download", "Upload")]
    [string]$Action
)

# Executes once before the first pipeline object is processed.
Begin {
    # We'll be working with .NET classes, so set the .NET working folder to ours
    # to make relative paths behave as expected in uploads and downloads.
    [System.IO.Directory]::SetCurrentDirectory(((Get-Location -PSProvider FileSystem).ProviderPath))
    $webclient = New-Object System.Net.WebClient
    $webclient.Credentials = New-Object System.Net.NetworkCredential($UserName, $Password)
}

# Executes once per pipeline object.
Process {
    switch ($Action) {
        "Download" { $webclient.DownloadFile("$ServerPath/$FileName", "$LocalPath/$FileName") }
        "Upload" { $webclient.UploadFile("$ServerPath/$FileName", "$LocalPath/$FileName") }
    }
}

# Executes once after the last pipeline object is processed.
End {
    # Nothing to clean up. No need to Dispose() the WebClient.
}