Beware of Invoke-WebRequest in PowerShell DSC

PowerShell has a handy cmdlet named Invoke-WebRequest. I was making use of this in a Script resource as part of a DSC script.

The weird thing was that most of the time it worked, but sometimes the DSC script hung, and as best I could tell, it was within the Script resource that was calling Invoke-WebRequest, but I couldn’t understand why.

Eventually on one particular server, I was able to cause something surprising to happen – calling Invoke-WebRequest caused a modal dialog to appear. The interesting thing was that the server had Internet Explorer Enhanced Security Configuration enabled. Not surprisingly that’s the default for Windows Server.

I posted a question to Stack Overflow and a comment added to the answer made me realise what is actually going on.

I had naively assumed that Invoke-WebRequest is just a nice wrapper around the .NET Framework’s WebClient class, but it turns out it is a bit more than that. It also appears to reference IE-related code.

If you’re curious as to what Invoke-WebRequest actually does, then fire up your favourite IL decompiler and point it at C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Microsoft.PowerShell.Commands.Utility\v4.0_3.0.0.0__31bf3856ad364e35\Microsoft.PowerShell.Commands.Utility.dll (that’s the path I found the full assembly at).

While the implementation of Invoke-WebRequest actually uses System.Net.WebRequest, it also creates an instance of the IHTMLDocument2 COM object, and I suspect this is the trigger that causes the IE warning to appear.

So if you just want to hit a web address without requiring all the extra features of IE processing, just call either WebClient or WebRequest directly from PowerShell, or Use Invoke-WebRequest but probably not in a ‘headless’ environment.

Structured JavaScript within ASP.NET MVC

First off, run (don’t walk) and go and register for next week’s ADNUG talk.

Done that?

Great, I’ll see next Wednesday evening!

What? You need more convincing? Ok..

I’ve worked with Ben Laan for a number of years now and I’d have to say he’s probably one of THE best developers I know around the place. He seriously knows his stuff, and is just as comfortable optimising a SQL query on the back-end as he is tweaking CSS layout in the frond-end UI. So I was really pleased when he agreed to come and speak at next week’s Adelaide .NET User Group (ADNUG).

To quote from the presentation summary:

Modern web development calls for more JavaScript than ever before. Loose, unorganised script files are no longer acceptable – or sometimes manageable. It is important to ensure those scripts are logically organised, structured, and testable, to ensure code quality.

This presentation will review techniques for organising code to meet these goals within an ASP.NET MVC context using RequireJs – a system for dependency management and Qunit – a unit test framework build by the JQuery team.

Ben’s been living and breathing this stuff recently, so I know it’s going to be a really good evening. Even if you don’t do .NET I think you’ll pick up a lot of tips on the writing better JavaScript.

So now I’ve convinced you, go and register and I’ll see you at there 😀

ADNUG meets monthly on the second Wednesday of the month, at Marcellina Adelaide (273 Hindley St, Adelaide). Pizza from 6pm followed by presentation(s), finishing around 7.30pm

An inspiring afternoon

This afternoon I attended a funeral. The church was packed with friends and family, I have to say it was one of the best celebrations of someone’s life that I’ve been privileged to attend.

Yes, there was sadness and grief, but overwhelmingly a sense of joy of a life well lived - a passionate husband, father, and faithful man of God.

In his late 50’s, John was not an old man when he passed away last week, but the impact his life and love for others will continue to be felt for years to come.