MS Support for XSLT >1.0
Sadly MS took the decision not to provide support for XSLT > 1.0. Here's their reasoning from 2004; and so far as I can see it's not been revised since.
https://blogs.msdn.microsoft.com/dareobasanjo/2004/05/13/why-you-wont-see-xslt-2-0-or-xpath-2-0-in-the-next-version-of-the-net-framework/
There are several reasons why we aren’t implementing XSLT 2.0 and XPath 2.0.
It takes a lot of effort...
Their XslCompiledTransform
does support some additional features over XSLT 1.0; but it's non-standard and by no means full support.
https://msdn.microsoft.com/en-us/library/system.xml.xsl.xslcompiledtransform(v=vs.110).aspx
The XslCompiledTransform class is an XSLT processor that supports the XSLT 1.0 syntax. It is a new implementation and includes performance gains when compared to the obsolete XslTransform class. The structure of the XslCompiledTransform class is very similar to the XslTransform class. The Load method loads and compiles the style sheet, while the Transform method executes the XSLT transform.
Workaround: Use a 3rd Party solution: e.g. Saxon
That said, in BT you can make use of C# classes within orchestrations. Saxon provides support for XSLT 3.0 for .net, so you just need to make use of their third party library. Here's a getting started guide:
http://www.saxonica.com/html/documentation/about/gettingstarted/gettingstarteddotnet.html
Feature Request
There is an open issue on the .Net Core Framework
site requesting this support. Once it's in the framework, BT would surely make use of it. Please thumbs up
this suggestion to help prioritise it: https://github.com/dotnet/corefx/issues/2295