The content of the XPath matching node is blank (inner text is blank)

The requirement is to write the XPath that can retrieve the node with the title content (inner text) empty from the following XML:

<?xml version="1.0" encoding="utf-8" ?><BookCatalog><Books><Book><Title>Asp.net</Title><Price>22.5</Price><Author>Abraham</Author></Book><Book><Title></Title><Price>22.5</Price><Author>Abraham</Author></Book></Books></BookCatalog>

The XPath statements that are easy to write are as follows:

//Book[Title[text()='']] //Book[Title[text() is null]] //Book[Title[node() is null]] //Book[Title[. is null]] //Book[Title[text()=]] 

The correct syntax is as follows:

// Book [title [not (text ()] or // book [title [not (node ()]

The validators are:

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Xml;namespace TestXPath{    class Program    {        static void Main(string[] args)        {            string[] errorXPaths = { "//Book[Title[text()='']]",                 "//Book[Title[text() is null]]",                 "//Book[Title[node() is null]]",                 "//Book[Title[. is null]]",                "//Book[Title[text()=]]"};            string[] correctXPaths = { "//Book[Title[not(text())]]", "//Book[Title[not(node())]]" };            string xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?> " + @"                        <BookCatalog>                        <Books>                        <Book>                        <Title>Asp.net</Title>                        <Price>22.5</Price>                        <Author>Abraham</Author>                        </Book>                        <Book>                        <Title></Title>                        <Price>22.5</Price>                        <Author>Abraham</Author>                        </Book>                        </Books>                        </BookCatalog>";            XmlDocument xmlDocument = new XmlDocument();            xmlDocument.LoadXml(xml);            foreach (string errorxPath in errorXPaths)            {                try                {                    XmlNodeList nodeList = xmlDocument.SelectNodes(errorxPath);                    Console.WriteLine("errorxPath:" + errorxPath);                    Console.WriteLine("nodeList.Count:" + nodeList.Count);                }                catch (Exception ex)                {                    Console.WriteLine(ex.Message);                }             }            foreach (string correctXPath in correctXPaths)            {                XmlNodeList nodeList = xmlDocument.SelectNodes(correctXPath);                Console.WriteLine("correctXPath:" + correctXPath);                Console.WriteLine("nodeList.Count:" + nodeList.Count);            }            Console.Read();        }    }}