The new build system which was introduced in Visual Studio Team Services (VSTS) and TFS 2015 has been gaining more popularity lately, and (in my opinion) rightly so. It simply works far better than the old XAML builds. I’ve been converting quite a few XAML based builds to the new build system. While doing this, I (inevitably of course) came across quite a few custom build workflows and tasks. Some of these were easily converted to build tasks that are available out-of-the-box, while others required some custom tasks. When creating a custom build or a custom build task, you’ll at some point need some build-specific information. This is where environment variables become necessary. Since I wasn’t too familiar with the concept (I’d heard of them, but never really used them) I decided to dig a little deeper.