This entry covers several separate problems in the implementation of extension functions on .NET.
(1) In XQuery, extension functions written in Java do not work on .NET. This applies both to user-written extension functions, and to those Saxon extension functions which are written as standard extension functions. (It does not apply to some extensions such as saxon:evaluate() which are given special treatment in the code)
(2) Extension functions taking an array as one of their arguments do not work.
(3) Declaring a first argument of type net.sf.saxon.expr.XPathContext does not work. (It wasn't actually certified to work, but the code is pretty close to it and it seemed worth fixing).
Fixes for all three problems are being placed in Subversion and will be included in a maintenance build of the .NET product in due course.