对如何解析带有命名空间前缀的 xml 感到非常困惑

问：

因此，我需要能够解析可能包含命名空间前缀的 xml 文件。我尝试使用示例文件执行此操作，并且在尝试获取节点列表时，即使我指定了一个没有属性前缀的节点，它也会返回 null。

我一直在尝试对此进行研究，它不断回到这样一个事实，即如果不定义命名空间前缀，它将无法工作，因此我添加了我认为可以执行此操作的代码，但它仍然给出相同的结果。这是我添加的一些代码：

protected void Page_Load(object sender, EventArgs e)
{
    xml.Load(Server.MapPath("~/SomeLesson/imsmanifest.xml"));
    populateBaseNodes();
}

private void populateBaseNodes()
{
    treeViewMenu.Nodes.Clear(); // Clear any existing items
    TreeNode treenode = new TreeNode();
    treenode.Text = "organizations";
    XmlNodeList baseNodeList;

    string xmlns = xml.DocumentElement.Attributes["xmlns"].Value;
    XmlNamespaceManager nsmgr = new XmlNamespaceManager(xml.NameTable);
    nsmgr.AddNamespace("adlcp", "http://www.adlnet.org/xsd/adlcp_v1p3");
    nsmgr.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
    nsmgr.AddNamespace("imscp", "http://www.w3.org/2001/XMLSchema-instance");
    nsmgr.AddNamespace("imsss", "http://www.w3.org/2001/XMLSchema-instance");
    nsmgr.AddNamespace("schemaLocation", "http://www.w3.org/2001/XMLSchema-instance");

    baseNodeList = xml.SelectNodes("/manifest/organizations/organization/item", nsmgr);

    TextBox1.Text = baseNodeList.Count.ToString();

    foreach (XmlNode xmlnode in baseNodeList)
    {
        TreeNode treeNodeCatalog = new TreeNode();
        treeNodeCatalog.Text = xmlnode.Attributes["identifier"].Value;
        treeNodeCatalog.SelectAction = TreeNodeSelectAction.Expand;
        treeViewMenu.Nodes.Add(treeNodeCatalog);
    }

    treeViewMenu.CollapseAll();
}

（marc_s）下面是需要解析的有问题的 XML：

<manifest identifier="Navigating_in_QuickBooks_-_Introduction_MANIFEST" version="1.3"
  xmlns="http://www.imsglobal.org/xsd/imscp_v1p1"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:imscp="http://www.imsglobal.org/xsd/imscp_v1p1"
    xmlns:adlcp="http://www.adlnet.org/xsd/adlcp_v1p3" 
    xmlns:imsss="http://www.imsglobal.org/xsd/imsss"
    xsi:schemaLocation=" http://www.imsglobal.org/xsd/imscp_v1p1 imscp_v1p1.xsd
                         http://www.imsglobal.org/xsd/imsss imsss_v1p0.xsd
                         http://www.adlnet.org/xsd/adlcp_v1p3 adlcp_v1p3.xsd 
                         http://www.adlnet.org/xsd/adlseq_v1p3 adlseq_v1p3.xsd
                         http://www.adlnet.org/xsd/adlnav_v1p3 adlnav_v1p3.xsd">

  <metadata>  
     <!-- not relevant here ... -->
  </metadata>
  <organizations default="TOC1">
     <organization identifier="TOC1">
        <title>Navigating in QuickBooks - Introductory Lesson</title>
        <item identifier="I_SCO0" identifierref="SCO0"> 
            <title>Navigating in QuickBooks - Introductory Lesson</title>
        </item>
     </organization>
   </organizations>
   <resources>
     <!-- not relevant here ... -->
   </resources>
</manifest>