Short blog post with instructions: https://kpitsimpl.blogspot.com/2018/04/t-sql-for-xml-and-net-for-xslt.html
Keys for turning SQL to XML and transforming with .NET:
1). Get your SQL data (assuming you are using SQL Server) into XML format via T-SQL FOR XML or the like on alternate db server.
2). Load XSL transform file (OrderXform.xsl) into a new XslCompiledTransform object (transform)
3). Using a StringWriter (writer), StringReader (inputReader) and XmlReader (inputXmlReader), read the inputReader XML string into inputXmlReader and apply the XSL transformation to the transform object via: transform.Transform(inputXmlReader, args, writer); //(or another override of Transform())
4). Return the result and write the bits (to application memory as Label Text for a demo/walktrough like this, to domain network location, to non-domain customer ftp, etc.).