Is it possible to perform a transform on multiple input XML files?
It doesn't appear to be possible using XslCompiledTransform, but is there an alternative way of applying an XSLT?
You can use the XSL function document() in your XSLT to reference an external XML file.
document().Apply the transformation to each input XML file individually and compose the resulting XML documents into a single document.
Compose the input XML files into a single document and apply the transformation, e.g.
XElement root = new XElement("root",
XElement.Load("file1.xml"),
XElement.Load("file2.xml"),
XElement.Load("file3.xml"));
XslCompiledTransform transform;
transform.Transform(root.CreateReader(), output);