Loading PowerShell snap-ins from a script

So I wanted to launch an Exchange Management Shell (EMS) script to do some stuff for a project at work. Normally this would be straightforward, but because of the way our virtualized lab environment works, it took me some fiddling to get it working.

What I needed to do was something like this:

c:\windows\system32\powershell\v1.0\powershell.exe -command "someStuff"

That worked fine as long as all I wanted to do was run basic PowerShell cmdlets. Once I started trying to run EMS cmdlets, things got considerably more complex because I needed a full EMS environment. First I had to deal with the fact that EMS, when it starts, tries to perform a CRL check. On a non-Internet-connected system, it will take 5 minutes or so to time out. I had completely forgotten this, so I spent some time fooling around with various combinations of RAM and virtual CPUs trying to figure out what the holdup was. Luckily Jeff Guillet set me straight when he pointed me to this article, helpfully titled “Configuring Exchange Servers Without Internet Access.” That cut the startup time waaaaay down.

However, I was still having a problem: my scripts wouldn’t run. They were complaining that “No snap-ins have been registered for Windows PowerShell version 2”. What the heck? Off to Bing I went, whereupon I found that most of the people reporting similar problems were trying to launch PowerShell.exe and load snap-ins from web-based applications. That puzzled me, so I did some more digging. Running my script from the PowerShell session that appears when you click the icon in the quick launch bar seemed to work OK. Directly running the executable by its path (i.e. %windir%\system32\powershell\v1.0\powershell.exe) worked OK too… but it didn’t work when I did the same thing from my script launcher.

Back to Bing I went. On about the fifth page of results, I found this gem at StackExchange. The first answer got me pointed in the right direction. I had completely forgotten about file system virtualization, the Windows security feature that, as a side effect, helps erase the distinction between x64 and x86 binaries by automatically loading the proper executable even when you supply the “wrong” path. In my case, I wanted the x64 version of PowerShell, but that’s not always what I was getting because my script launcher is a 32-bit x86 process. When it launched PowerShell.exe from any path, I was getting the x86 version, which can’t load x64 snap-ins and thus couldn’t run EMS.

The solution? All I had to do was read a bit further down in the StackExchange article to see this MSDN article on developing applications for SharePoint Foundation, which points out that you must use %windir%\sysnative as the path when running PowerShell scripts after a Visual Studio build. Why? Because Visual Studio is a 32-bit application, but the SharePoint snap-in is x64 and must be run from an x64 PowerShell session… just like Exchange.

Armed with that knowledge, I modified my scripts to run PowerShell using sysnative vice the “real” path and poof! Problem solved. (Thanks also to Michael B. Smith for some bonus assistance.)