XML文檔操作集錦(C#篇)，

XML文檔操作集錦(C#篇)，

　　在JSON沒流行起來的時候xml一直作為程序存儲配置信息的主流介質；特別是小型數據表方面還是不錯的選擇，所以經常涉及到的操作無非也就是增刪改查，這篇博客主要是對這些對比較常用的操作做了個簡單的總結

文件加載

SelectNodes()、SelectSingleNode()節點獲取大法

創建XML文檔及設置元素值

XmlReader與XmlWriter

DataSet與XML數據

Linq to XML

XML序列化與反序列化

文件加載

•  通過路徑加載XML

   XmlDocument xmlDoc = new XmlDocument();
   xmlDoc.Load(fileName);//文件路徑或者URL地址
   Console.WriteLine(xmlDoc.InnerXml);
   Console.WriteLine("==============有逼格的分割線================");
   xmlDoc.Load("http://feed.cnblogs.com/blog/picked/rss");//博客園精華帖RSS
   Console.WriteLine(xmlDoc.InnerXml);

• 通過文件流加載

   using (FileStream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read))
   {
       XmlDocument xmlDoc = new XmlDocument();
       xmlDoc.Load(stream);
       Console.WriteLine(xmlDoc.InnerXml);
   }

　　Load()方法還重載了一些方法，並且還有別的方式可以加載XML文檔，比如LoadXml()直接加載一段XML串

SelectNodes()、SelectSingleNode()節點獲取大法

<?xml version="1.0" encoding="utf-8" ?> <Names> <Name> <FirstName>John</FirstName> <LastName>Smith</LastName> </Name> <Name> <FirstName>James</FirstName> <LastName>White</LastName> </Name> </Names> XML文件

• 通過XPath表達式的SelectNodes(string xpath)方法獲取節點列表；SelectSingleNode(string xpath)獲取第一個匹配的節點

    XmlNodeList xmlNodes = xmlDoc.SelectNodes("/Names/Name");//第一個斜槓必須是根節點
    foreach (XmlNode item in xmlNodes)
    {
        Console.WriteLine(item.InnerXml);
    }
    Console.WriteLine("==================================");
    XmlNode xmlNode = xmlDoc.SelectSingleNode("/Names/Name");
    Console.WriteLine(xmlNode.InnerXml);
    Console.WriteLine(xmlNode["LastName"].InnerText);//獲取子節點

• 設置節點特性值查找節點

<Root>
  <Item Id="1"  Grade="1">張三</Item>
  <Item Id="2"  Grade="1">李四</Item>
  <Item Id="3"  Grade="2">王五</Item>
  <Item Id="4"  Grade="3">趙六</Item>
</Root>

  XmlNodeList xmlNodes = xmlDoc.SelectNodes("/Root/Item[@Grade='1']");//XPath表達式獲取設置要獲取節點的特性值信息
  foreach (XmlNode item in xmlNodes)
  {
      Console.WriteLine(item.InnerText);
  }

• 獲取第N個節點

   XmlNode xmlNode = xmlDoc.SelectSingleNode("/Root/Item[position()=3]");//獲取第N個節點（根據XML節點的順序）
   Console.WriteLine(xmlNode.InnerText);
   Console.WriteLine("==============================");
   XmlNodeList xmlNodes = xmlDoc.SelectNodes("/Root/Item[position()<=3]");//獲取從第一個到第N個的節點（根據XML節點的順序
   foreach (XmlNode item in xmlNodes)
   {
       Console.WriteLine(item.InnerText);
   }
   Console.WriteLine("==============================");
   xmlNodes = xmlDoc.SelectNodes("/Root/Item[position() > 2]");//獲取大於第N個的節點（根據XML節點的順序）
   foreach (XmlNode item in xmlNodes)
   {
       Console.WriteLine(item.InnerText);
   }

創建XML文檔及設置元素值

   XmlDocument xmlDoc = new XmlDocument();
   XmlNode rootNode = xmlDoc.CreateElement("Root");//創建一個節點
   xmlDoc.AppendChild(rootNode);
   Console.WriteLine(xmlDoc.InnerXml);
   Console.WriteLine("==============有逼格的分割線================");

   XmlNode node = xmlDoc.CreateElement("Item");
   XmlAttribute attribute = xmlDoc.CreateAttribute("Id");//創建節點特性
   attribute.Value = "1";//設置特性值
   node.Attributes.Append(attribute);
   node.InnerText = "張三";
   rootNode.AppendChild(node);
   Console.WriteLine(xmlDoc.InnerXml);
   Console.WriteLine("==============有逼格的分割線================");
   node = xmlDoc.CreateElement("Item");
   attribute = xmlDoc.CreateAttribute("Id");
   attribute.Value = "2";
   node.Attributes.Append(attribute);
   node.InnerText = "李四";
   rootNode.AppendChild(node);
   Console.WriteLine(xmlDoc.InnerXml);
   xmlDoc.Save(fileName);//保存到文件

 XmlReader與XmlWriter

　　XmlReader操作XML比XmlDocument更快、內存消耗更少(可以寫一個測試驗證一下)；但是它需要去手動判斷元素的類型，操作起來比XmlDocument稍微蛋疼一些

    using (XmlWriter xmlWriter = XmlWriter.Create(fileName))
    {
        xmlWriter.WriteStartDocument();//開始寫入xml文檔
        xmlWriter.WriteStartElement("users");
        xmlWriter.WriteStartElement("user");
        xmlWriter.WriteAttributeString("Id", "42");
        xmlWriter.WriteString("張三");
        xmlWriter.WriteEndElement();

        xmlWriter.WriteStartElement("user");
        xmlWriter.WriteAttributeString("Id", "39");
        xmlWriter.WriteString("李四");
        xmlWriter.WriteEndDocument();//結束寫入xml文檔
    }

    using (XmlReader xmlReader = XmlReader.Create(fileName))
    {
        while (xmlReader.Read())
        {
            if (xmlReader.NodeType == XmlNodeType.Element)//元素的類型
            {
                Console.WriteLine(xmlReader.Name);//元素名稱
                if (xmlReader.HasAttributes)
                {
                    Console.WriteLine(xmlReader.GetAttribute("Id"));//元素名稱
                }
                Console.WriteLine(xmlReader.ReadOuterXml());//獲取節點的所有子內容
            }
        }
    }

DataSet與XML數據

　　通過XmlReader將數據讀入到DataSet數據集中

   using (XmlReader xmlReader = XmlReader.Create(fileName, new XmlReaderSettings()))
   {
       DataSet ds = new DataSet();
       ds.ReadXml(xmlReader);
       DataTable dt = ds.Tables[0];
       for (int i = 0; i < dt.Rows.Count - 1; i++)
       {
           object[] items = dt.Rows[i].ItemArray;
           Console.WriteLine(string.Join(" ", items));
       }
   }

　 將數據表保存到XML文件也是比較常用的

   DataSet ds = new DataSet();
   DataTable dt = new DataTable();
   dt.Columns.Add(new DataColumn("Id", Type.GetType("System.Int32")));
   dt.Columns.Add(new DataColumn("Grade", Type.GetType("System.Int32")));
   dt.Columns.Add(new DataColumn("Name", Type.GetType("System.String")));

   DataRow dr = dt.NewRow();
   dr["Id"] = 9999;
   dr["Grade"] = 3;
   dr["Name"] = "孫七";
   dt.Rows.Add(dr);

   ds.Tables.Add(dt);
   ds.Tables[0].TableName = "Student";//每張表為根節點下的第一個子節點
   ds.WriteXml(fileName);

 Linq to XML

　　通過linq操作XML上手快、操作方便

  //查詢
  XDocument xdoc = XDocument.Load(fileName);
  var query = from item in xdoc.Descendants("Item")
              select new { Id = item.Attribute("Id").Value, Name = item.Value };
  foreach (var item in query)
  {
      Console.WriteLine(item.Id + " " + item.Name);
  }

 //添加
 XDocument xdoc = XDocument.Load(fileName);
 XElement xele = new XElement("Item","吳十?");//創建節點
 xele.SetAttributeValue("Id", 10);//設置節點特性值
 xdoc.Element("Root").Add(xele);
 xdoc.Save(fileName);

 //刪除
 XDocument xdoc = XDocument.Load(fileName);
 XElement xele = xdoc.Descendants("Item").Where(c => c.Attribute("Id").Value.Equals("10")).FirstOrDefault();
 xele.Remove();
 xdoc.Save(fileName);

  //修改
  XDocument xdoc = XDocument.Load(fileName);
  XElement xele = xdoc.Descendants("Item").Where(c => c.Attribute("Id").Value.Equals("1")).FirstOrDefault();
  xele.Value = "流年";
  xdoc.Save(fileName);

XML序列化與反序列化

 //序列化
 var student = new Student() { Id = 1, Grade = 2, Name = "王五" };
 XmlSerializer serializer = new XmlSerializer(typeof(Student));
 serializer.Serialize(Console.Out, student);

 //反序列化
 string input = "<?xml version=\"1.0\" encoding=\"gb2312\"?><student><Id> 1 </Id><Grade> 2 </Grade><Name> 李四 </Name></student>";
 using (StringReader sr = new StringReader(input))
 {
     XmlSerializer serializer = new XmlSerializer(typeof(Student));
     Student student = (Student)serializer.Deserialize(sr);
     Console.WriteLine(student.Name);
 }

擴展閱讀

http://www.dotnetcurry.com/linq/564/linq-to-xml-tutorials-examples
http://www.tutorialspoint.com/linq/linq_xml.htm
https://msdn.microsoft.com/en-us/library/mt693062.aspx
http://broadcast.oreilly.com/2010/10/understanding-c-simple-linq-to.html
http://www.codeproject.com/Articles/24376/LINQ-to-XML
http://csharp.net-tutorials.com/xml/reading-xml-with-the-xmlreader-class/
https://msdn.microsoft.com/zh-cn/library/58a18dwa(v=vs.120).aspx
http://csharp.net-informations.com/xml/xml-de-serialization.htm