A table-driven approach to creating SharePoint sites with PowerShell

While cleaning up some PowerShell installations scripts that I wrote some time ago, I come across the following piece of code (modified slightly for anonymity) for creating a hierarchy of SharePoint sites and setting the locale for a subset of the sites. It works but it sure doesn’t adhere to the DRY principle.

New-SPWeb -url $base_url -addtoquicklaunch -template "STS#1" -name "Base"
New-SPWeb -url $base_url/Dk -addtoquicklaunch -template "STS#1" -name "Dk"
New-SPWeb -url $base_url/Uk -addtoquicklaunch -template "STS#1" -name "Uk"
New-SPWeb -url $base_url/Dk/BusinessUnit1 -addtoquicklaunch -template "STS#1" -name "BusinessUnit1"  
New-SPWeb -url $base_url/Dk/BusinessUnit2 -addtoquicklaunch -template "STS#1" -name "BusinessUnit2"
New-SPWeb -url $base_url/Uk/BusinessUnit1 -addtoquicklaunch -template "STS#1" -name "BusinessUnit1"
New-SPWeb -url $base_url/Uk/BusinessUnit2 -addtoquicklaunch -template "STS#1" -name "BusinessUnit2"

$dk = Get-SPWeb $base_url/Dk
$dkBusinessUnit1 = Get-SPWeb $base_url/Dk/BusinessUnit1
$dkBusinessUnit2 = Get-SPWeb $base_url/Dk/BusinessUnit2

$locale = [System.Globalization.CultureInfo]::CreateSpecificCulture("da-DK")
$dk.Locale = $locale
$dk.Update()

$dkBusinessUnit1.Locale = $locale
$dkBusinessUnit1.Update()
  
$dkBusinessUnit2.Locale = $locale
$dkBusinessUnit2.Update()

How can we reduce this repetition? Well, it repeats because we’ve made the common mistake of mixing logic with data. One way to separate the two is using a table-driven approach, i.e., extract the varying parts, the data, into a table and rewrite the logic so it’s parameterized by the table. After some experimentation with PowerShell here’s the code I ended up with:

$sites = @( @("", "Base"), 
            @("Dk", "Dk", "da-DK"),
            @("Uk", "Uk"),
            @("Dk/BusinessUnit1", "BusinessUnit1", "da-DK"),
            @("Dk/BusinessUnit2", "BusinessUnit2", "da-DK"),
            @("Uk/BusinessUnit1", "BusinessUnit1"),
            @("Uk/BusinessUnit2", "BusinessUnit2") )

$sites | foreach {
  $url, $title, $culture = $_
  $newSite = New-SPWeb -url "$base_url/$url" -addtoquicklaunch -template "STS#1" -name $title
    
  if ($culture -ne "") {
    $locale = [System.Globalization.CultureInfo]::CreateSpecificCulture($culture)
    $newSite.Locale = $locale
    $newSite.Update()
  }
}

So far so good. The un-installation part of the script, however, follows the same pattern of repetition:

Remove-SPWeb -identity $base_url/Uk/BusinessUnit2 -confirm:$false -ErrorAction SilentlyContinue
Remove-SPWeb -identity $base_url/Uk/BusinessUnit1 -confirm:$false -ErrorAction SilentlyContinue
Remove-SPWeb -identity $base_url/Dk/BusinessUnit2 -confirm:$false -ErrorAction SilentlyContinue
Remove-SPWeb -identity $base_url/Dk/BusinessUnit1 -confirm:$false -ErrorAction SilentlyContinue
Remove-SPWeb -identity $base_url/Dk -confirm:$false -ErrorAction SilentlyContinue
Remove-SPWeb -identity $base_url/Uk -confirm:$false -ErrorAction SilentlyContinue
Remove-SPWeb -identity $base_url -confirm:$false

But now that we have the table of sites at hand, we can easily make the site removal table-driven as well:

function Reverse($array) {
  $clone = $array.Clone()
  [Array]::Reverse($clone)
  $clone
}

Reverse($sites) | foreach {
  $url = $_[0]  
  Remove-SPWeb -identity "$base_url/$url" -confirm:$false -ErrorAction SilentlyContinue
}

I’m sure the code could be written more elegantly, but given my working knowledge of PowerShell I’m satisfied with the result. I especially like the functional programming style.