What is the Linq.First equivalent in PowerShell?

Question

The snippet below detects from a list of files which of them is a Directory on Ftp

as C# it will be like below

var files = new List<string>(){"App_Data", "bin", "Content"}; var line = "drwxr-xr-x 1 ftp ftp              0 Mar 18 22:41 App_Data" var dir = files.First(x => line.EndsWith(x)); 

How I can transalte the last line in PowerShell ?

Answer 1

Something like this...

$files = @("App_Data", "bin", "Content") $line = "drwxr-xr-x 1 ftp ftp              0 Mar 18 22:41 App_Data" $dir = $files | Where { $line.EndsWith($_) } | Select -First 1 

These versions of the last line would all accomplish the same:

$dir = @($files | Where { $line.EndsWith($_) })[0]  $dir = $files | Where { $line.EndsWith($_) } | Select -index 0  $dir = $files | Where { $line.EndsWith($_) } | Select -First 1 

It was pointed out that the above is not exactly equivalent in behavior to Linq.First because Linq.First throws exceptions in two cases:

• Throws ArgumentNullException when source or predicate is null.
• Throws InvalidOperationException when source sequence is empty or no element satisfies the condition in predicate.

If you wanted that behavior exactly, you'd need some extra guard code.

Answer 2

as Robert Groves said, Select-Object -First Occurence do the tricks, you can also use -Last Occurence.

by the way, like any other static .Net method you can use linq in powershell.

[Linq.Enumerable]::First($list)  [Linq.Enumerable]::Distinct($list)  [Linq.Enumerable]::Where($list, [Func[int,bool]]{ param($item) $item -gt 1 })