XML schema for ASPX?

I'm editing a lot of .aspx files in Emacs these days. nxml-mode can use a schema (RELAX NG, but maybe others) to detect errors in XML, and I find it really handy for other things.

Is there a RELAX NG schema for *.aspx files?

(I'm having trouble searching because "aspx" is so common not just as a language but as part of URLs.)

From stackoverflow

• I don't think ASPX is an XML format. I think <%@ is not valid XML, for example.