F＃Xml类型提供程序测试节点是否存在

This seems like it should be trivial. I'm parsing many XML files, some of which contain all of the expected nodes, some of which do not. I need to be able to test for the existence of a node. I am using the F# Xml Type Provider. This code does not work but it illustrates what I am trying to do.This seems like it should be trivial. I'm parsi