Suggestion: Add #Requires -Assembly AssemblyName support

[brianary]

Currently, if I want to reference a .NET assembly like System.Configuration, I do something like this at the top of my scripts:

try{[void][Configuration.ConfigurationManager]}catch{Add-Type -AN System.Configuration}

it would be much more readable (and declarative) as something like:

#Requires -Assembly System.Configuration

[PetSerAl]

Why do you put Add-Type in catch? You could also put using assembly System.Configuration on top of script.

[JasonG-STCU]

I, too, have used this in a script of mine. It would absolutely be beneficial to be able to include it this way.

[brianary]

@PetSerAl I wasn't aware of the using keyword, though I don't see assembly documented as an argument to it. Also, our servers are not uniformly on PowerShell 5 just yet, so that extended syntax isn't something we can fully rely on yet (my workstation is stuck on version 5.0.10105.0-April2015Preview which doesn't support using assembly, and I'm unable to upgrade or downgrade or uninstall it from Windows 7). It seems odd to have another thing that must come first in the script, along with [CmdletBinding()]Param(…). It looks like using must precede [CmdletBinding()]Param(…).

The reason I use the above formulation is to Add-Type only if referencing the type causes an exception, that way I'm only adding it once per session.

[PetSerAl]

The reason I use the above formulation is to Add-Type only if referencing the type causes an exception, that way I'm only adding it once per session.

You can not load same assembly twice anyway. No harm on calling Add-Type for already loaded assembly.

$a = Add-Type -AssemblyName System.Configuration -PassThru | Select-Object -First 1 -ExpandProperty Assembly
$b = Add-Type -AssemblyName System.Configuration -PassThru | Select-Object -First 1 -ExpandProperty Assembly
[Object]::ReferenceEquals($a, $b)

[brianary]

I'll have to look into the using syntax (I hope it gets added to the docs, and is officially supported) once I can finally upgrade things and get the new features.

However, even on a newer machine, there's a pretty big performance difference:

PS C:\Users\me> "$(Measure-Command {0..10000|% {iex 'using assembly System.Configuration'}})"
00:00:08.2655849
PS C:\Users\me> "$(Measure-Command {0..10000|% {Add-Type -AN System.Configuration}})"
00:00:04.6386843
PS C:\Users\me> "$(Measure-Command {0..10000|% {try{[void][Configuration.ConfigurationManager]}catch{Add-Type -AN System.Configuration}}})"
00:00:00.0728870

on my older machine, it's even bigger:

PS C:\Users\me> "$(Measure-Command {0..10000|% {Add-Type -AN System.Configuration}})"
00:00:08.1306933
PS C:\Users\me> "$(Measure-Command {0..10000|% {try{[void][Configuration.ConfigurationManager]}catch{Add-Type -AN System.Configuration}}})"
00:00:00.2983187

[rjmholt]

I've opened an RFC on updating the behaviour of #requires. Please feel free to comment in the PR.

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