一些常用的XPath语法
http://files.cnblogs.com/bear831204/XPathTest.zip
部分代码：
WriteElements("The root bookstore, this is the whole document:",
"./bookstore");
WriteElements("All <first-name> elements:",
".//first-name");
WriteElements("First <author> inside each <book>:",
".//book/author[1]");
WriteElements("Last <author> inside each <book>:",
".//book/author[last()]");
WriteElements("First <author> from the entire set of <author> elements within <book> elements:",
"(.//book/author)[1]");
WriteElements("First <author> inside first <book>:",
".//book[1]/author[1]");
WriteElements("All <author> elements that contain at least one <degree> element child and at least one <award> element child:",
".//author[degree and award]");
WriteElements("All <author> elements that contain at least one <degree> or <award> element and at least one <publication> element:",
".//author[(degree or award) and publication]");
WriteElements("The third <author> element that has a <first-name> child element:",
"(.//author[first-name])[3]");
WriteElements("All <book> elements whose style attribute value is equal to the specialty attribute value of the <bookstore> element at the root of the document:",
".//book[/bookstore/@specialty=@style]");
WriteElements("All <degree> elements one or more levels deep in the <bookstore> element (arbitrary descendants):",
"./bookstore//degree");
WriteElements("All elements with the style attribute:",
".//*[@style]");
WriteElements("First 2 <author> inside each <book>:",
".//book/author[position() < 3]");
WriteElements("All <author> elements that contain at least one <last-name> element child with the value Bob:",
".//author[last-name = 'Bob']");
WriteElements("All <author> elements that has a <last-name> child element with the value Bob and a <first-name> child element with the value Joe:",
".//author[last-name = 'Bob' and first-name = 'Joe']");
WriteElements("All <author> elements that do no contain <award> child elements with the value Pulitzer, inculding the author doesn't have award and has award but the value is not Pulitzer:",
".//author[not(award = 'Pulitzer')]");
WriteLog("The count of book element:" + " (count(.//book))");
WriteLog(_doc.XPathEvaluate("count(.//book)").ToString());
WriteLog();
WriteElements("All <author> elements that has a <first-name> child element with the value contains 'Ton':",
".//author[contains(first-name,'Ton')]");
WriteElements("All elements whose name contains st",
".//*[contains(name(),'st')]");
WriteElements("All first-name and last-name elements:",
".//*[name() = 'first-name' or name() = 'last-name']");
WriteElements("All elements whose name starts with publica:",
".//*[starts-with(name(),'publica')]");
WriteElements("All elements whose name starts with my:",
".//*[starts-with(name(),'my')]");
WriteElements("All elements whose local name is author:",
".//*[local-name()='author']");
WriteElements("All elements whose value is misery:",
".//*[.='misery']");
WriteElements("All <author> elements whose value is Matthew Bob:",
".//author[. = 'Matthew Bob']");
WriteElements("All author elements containing any child element whose value is Bob:",
".//author[* = 'Bob']");