使用过滤器获取 xml 节点

Question

我有下一个 xml：

<Histories>
  <History>
    <Date>2011.11.11 08:45</Date>
    <Action>Add</Action>
  </History>
  <History>
    <Date>2011.11.12 08:45</Date>
    <Action>Modify</Action>
  </History>
  <History>
    <Date>2011.11.13 08:45</Date>
    <Action>Delete</Action>
  </History>
  <History>
    <Date>2011.11.14 08:45</Date>
    <Action>Add</Action>
  </History>
  <History>
    <Date>2011.11.15 08:45</Date>
    <Action>Modify</Action>
  </History>
  <History>
    <Date>2011.11.16 08:45</Date>
    <Action>Delete</Action>
  </History>
  <History>
    <Date>2011.11.17 08:45</Date>
    <Action>Add</Action>
  </History>
  <History>
    <Date>2011.11.18 08:45</Date>
    <Action>Modify</Action>
  </History>
  <History>
    <Date>2011.11.19 08:45</Date>
    <Action>Delete</Action>
  </History>
  <History>
    <Date>2011.12.20 08:45</Date>
    <Action>Modify</Action>
  </History>
</Histories>

我需要通过操作（添加/修改/删除）获取最后一个节点。我能怎么做？

例子：

添加 2011.11.17 08:45

修改2011.12.20 08:45

删除2011.11.19 08:45

我这样做：/Histories/History/Action[text()='Add']/../../History[position()=last()] - 它不起作用。

谢谢

Answer 1

使用：

/*/History[Action = 'Delete'] [last()]

这会选择最后一个 History 元素，该元素有一个子 Action，字符串值为 "Delete"，并且（History 元素）是 XML 文档顶部元素的子元素。

Answer 2

$arr = array('Add','Modify','Delete');
foreach ($arr as $action) {
    $res = $xPath->query('/Histories/History[Action="'.$action.'"][last()]/Date');
    echo "Last $action: " . $res->item(0)->nodeValue . "\n";
}

编辑：以下是简洁的回复：/Histories/History[Action="Add"][last()]/Date

Answer 3

考虑使用linq to XML

辅助方法：

string GetValue(XDocument xDocument, string action)
{
    var xElements = xDocument.Descendants("Action").Where(x => x.Value == action);
    var xElement = xElements.Last().Parent;
    return xElement.Element("Date").Value;
}

用法：

var xml = @"<Histories>
  <History>
    <Date>2011.11.11 08:45</Date>
    <Action>Add</Action>
  </History>
...
  <History>
    <Date>2011.12.20 08:45</Date>
    <Action>Modify</Action>
  </History>
</Histories>";

var xDocument = XDocument.Parse(xml);

var lastAdd= GetLast(xDocument, "Add");
var lastModify = GetLast(xDocument, "Modify");
var lastDelete = GetLast(xDocument, "Delete"); 

string GetLast(XDocument xDocument, string action)
{
    var xElements = xDocument.Descendants("Action").Where(x => x.Value == action);
    var xElement = xElements.Last().Parent;
    return xElement.Element("Date").Value;
} 

Answer 4

public void insertToDo(string item, string date, string time, string due, string description)
        {
            XElement xEmp = XElement.Load(@"C://Users//Khulu//Documents//Visual Studio 2012//Projects//AMD//Schedule//ToDo.xml");
            //
            xEmp.Add(
                     new XElement("ToDo",
                      new XElement("Item", item),
                       new XElement("date", date),
                        new XElement("time", time),
                        new XElement("due", due),
                        new XElement("description", description))
            );
            xEmp.Save(@"C://Users//Khulu//Documents//Visual Studio 2012//Projects//AMD//Schedule//ToDo.xml");
        }
        public DataSet displayGrid()`enter code here`
        {
            DataSet ds = new DataSet();
            ds.ReadXml("C://Users//Khulu//Documents//Visual Studio 2012//Projects//AMD//Schedule//ToDo.xml");
            return ds;
        }
        public void deleteXml(string item)
        {
            XDocument doc = XDocument.Load("C://Users//Khulu//Documents//Visual Studio 2012//Projects//AMD//Schedule//ToDo.xml");
            doc.Root.Elements("ToDo")
            .Elements("Item")
            .Where(l => l.Value == item)
            .Select(x => x.Parent)
            .Remove();
            doc.Save("C://Users//Khulu//Documents//Visual Studio 2012//Projects//AMD//Schedule//ToDo.xml");
        }
        public void updateTodo(string item, string date, string time, string due, string description)
        {

            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.Load("C://Users//Khulu//Documents//Visual Studio 2012//Projects//AMD//Schedule//ToDo.xml");

            foreach (XmlNode node in xmlDoc.SelectNodes("toDoList/ToDo"))
            {
                if (node.SelectSingleNode("Item").InnerText == item)
                {
                    node.SelectSingleNode("Item").InnerText = item;
                    node.SelectSingleNode("date").InnerText = date;
                    node.SelectSingleNode("time").InnerText = time;
                    node.SelectSingleNode("due").InnerText = due;
                    node.SelectSingleNode("description").InnerText = description;

                }

            }
           xmlDoc.Save("C://Users//Khulu//Documents//Visual Studio 2012//Projects//AMD//Schedule//ToDo.xml");
        }

    }
}