XsltCompiledTransform.Transform with XmlReader/XmlWriter

Question

Hi - there is one form of the XsltCompiledTransform class's Transform() function that takes an XmlReader and XmlWriter as parameters:
https://msdn.microsoft.com/en-us/library/ms163433%28v=vs.110%29.aspx
At first glance, this would appear to allow a streaming-based transform of the input XML, without having to load the whole XML document into memory first.
But doing an XSLT transform is something very difficult to do in a streaming fashion (which XmlReader/XmlWriters would allow you to do).
So, I assume whilst this form of the function takes these streaming XML reader/writer classes, in reality it still loads the XML pointed to by the XmlReader completely into memory first, performs the transform, then writes out the whole document to the XmlWriter?
It doesn't say whether it loads the whole document into memory before transforming it in the MSDN docs...

Answer 1

Hi Herro, thanks for your response.
Sorry if my initial question wasn't clear - I don't know if the XsltCompiledTransform.Transform() function always loads the complete XML document into memory before transforming or not, that's what I'm asking.
The Transform(XmlReader, XmlWriter) form of the function is passed an XmlReader to read the XML to transform. An XmlReader does not have to load the complete XML document into memory in order to read any of its contents - it can read it part by part, tag
by tag in a forward-only fashion (in contrast to, say, XDocument or XmlDocument which loads the complete XML into a DOM tree).
If you use this form of the Transform(XmlReader, XmlWriter) method, my question is does this method still load the whole XML document into memory first before transforming the document and writing out the transformed XML using the XmlWriter?
To put it in a nutshell, is it possible to use XSLTs on large XML documents without loading the complete (large) XML document into memory first? Does this method load the whole document into memory first before performing the transform?