XmlDocument.SelectNodes 不起作用

今天采用Xpath读取Xml节点，怎么都读不出。

问题分析：

错误代码如下：

      XmlDocument xmlD = new XmlDocument();
      xmlD.PreserveWhitespace = true;
      xmlD.LoadXml(xStr);
      xmlD.SelectNodes(@"job-scheduling-data/schedule/job");

经排查 dotnet 文档，发现代码编写没有问题。文档描述如下：

文档示例如下：
示例代码：

using System;
using System.IO;
using System.Xml;

public class Sample
{
  public static void Main()
  {

      XmlDocument doc = new XmlDocument();
      doc.Load("booksort.xml");

      //Create an XmlNamespaceManager for resolving namespaces.
      XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
      nsmgr.AddNamespace("bk", "urn:samples");

      //Select and display the value of all the ISBN attributes.
      XmlNodeList nodeList;
      XmlElement root = doc.DocumentElement;
      nodeList = root.SelectNodes("/bookstore/book/@bk:ISBN", nsmgr);
      foreach (XmlNode isbn in nodeList){
        Console.WriteLine(isbn.Value);
      }
   }
}

示例XML：

<bookstore xmlns:bk="urn:samples">
  <book genre="novel" publicationdate="1997" bk:ISBN="1-861001-57-8">
    <title>Pride And Prejudicetitle>
    <author>
      <first-name>Janefirst-name>
      <last-name>Austenlast-name>
    author>
    <price>24.95price>
  book>
  <book genre="novel" publicationdate="1992" bk:ISBN="1-861002-30-1">
    <title>The Handmaid's Taletitle>
    <author>
      <first-name>Margaretfirst-name>
      <last-name>Atwoodlast-name>
    author>
    <price>29.95price>
  book>
  <book genre="novel" publicationdate="1991" bk:ISBN="1-861001-57-6">
    <title>Emmatitle>
    <author>
      <first-name>Janefirst-name>
      <last-name>Austenlast-name>
    author>
    <price>19.95price>
  book>
  <book genre="novel" publicationdate="1982" bk:ISBN="1-861001-45-3">
    <title>Sense and Sensibilitytitle>
    <author>
      <first-name>Janefirst-name>
      <last-name>Austenlast-name>
    author>
    <price>19.95price>
  book>
bookstore>

自己程序采用Xml：

结论：问题原因：最后用文档示例与自己代码比较发现上命名空间导致**

修改后正确代码

     string xStr = File.ReadAllText(path.Trim());
                xStr = xStr.Replace("", "");
                xStr = xStr.Replace("xmlns=\"http://quartznet.sourceforge.net/JobSchedulingData\"", "");
                xStr = xStr.Replace("xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"", "");
                XmlDocument xmlD = new XmlDocument();
                xmlD.PreserveWhitespace = true;
                xmlD.LoadXml(xStr);
                XmlNodeList jobNodeList = xmlD.SelectNodes(@"job-scheduling-data/schedule/job");