In the past, BizTalk (and the .NET framework in general) has not supported any XSLT version besides 1.0. Our company is about to upgrade to BizTalk Server 2016, and I was wondering whether it's possible (and natively supported) to use XSLT 2.0 or 3.0 for custom mapping in said BizTalk Server version?
I know it's not likely they've implemented this, but I've been roaming the internet and I can't seem to find a concrete answer to this question.
No, it only supports XSLT 1.0.
However it has been requested on uservoice before it was decommissioned
And Microsoft responded
Tord Glad Nordahl (Program Manager, Microsoft Corp) responded · March 18, 2017 We have forwarded this request to the .NET team. We will keep this open.
XSLT 3 is however a feature with BizTalk 2020, see What's New in BizTalk Server 2020.
XSLT 3.0 New extensible model for runtime map execution, out of box wiring to work with Saxon XSLT3.0.