XML数据读取方式性能比较（一）

　　测试开始先读取XML源，用一个比较大的rss文件链接，复制到项目bin/debug目录下。

Stream xmlStream = new MemoryStream(File.ReadAllBytes(path));

　　一、XmlDocument 方式

代码

1 static IList testXmlDocument()
 2 {
 3     var doc = new XmlDocument();
 4     doc.Load(xmlStream);
 5     var nodeList = doc.DocumentElement.ChildNodes;
 6     var lstChannel = new List<Object>(nodeList.Count );
 7     foreach (XmlNode node in nodeList)
 8     {
 9         var channel = new
10         {
11             Title = node.SelectSingleNode("title").InnerText,
12             Link = node.SelectSingleNode("link").InnerText,
13             Description = node.SelectSingleNode("description").InnerText,
14             Content = node.SelectSingleNode("content").InnerText,
15             PubDate = node.SelectSingleNode("pubDate").InnerText,
16             Author = node.SelectSingleNode("author").InnerText,
17             Category = node.SelectSingleNode("category").InnerText
18         };
19         lstChannel.Add(channel);
20     }
21     return lstChannel;
22 }

　　二、XPathNavigator 方式

代码

1 static IList testXmlNavigator()
 2 {
 3     var doc = new XmlDocument();
 4     doc.Load(xmlStream);
 5     var nav = doc.CreateNavigator();
 6     nav.MoveToRoot();
 7     var nodeList = nav.Select("/channel/item");
 8     var lstChannel = new List<Object>(nodeList.Count);
 9     foreach (XPathNavigator node in nodeList)
10     {
11         var channel = new
12         {
13             Title = node.SelectSingleNode("title").Value,
14             Link = node.SelectSingleNode("link").Value,
15             Description = node.SelectSingleNode("description").Value,
16             Content = node.SelectSingleNode("content").Value,
17             PubDate = node.SelectSingleNode("pubDate").Value,
18             Author = node.SelectSingleNode("author").Value,
19             Category = node.SelectSingleNode("category").Value
20         };
21         lstChannel.Add(channel);
22     }
23     return lstChannel;
24 }

　　三、XmlTextReader 方式

代码

1 static List<Channel> testXmlReader()
 2 {
 3     var lstChannel = new List<Channel>();
 4     var reader = XmlReader.Create(xmlStream);
 5     while (reader.Read())
 6     {
 7         if (reader.Name == "item" && reader.NodeType == XmlNodeType.Element)
 8         {
 9             var channel = new Channel();
10             lstChannel.Add(channel);
11             while (reader.Read())
12             {
13                 if (reader.Name == "item") break;
14                 if (reader.NodeType != XmlNodeType.Element) continue;
15                 switch (reader.Name)
16                 {
17                     case "title":
18                         channel.Title = reader.ReadString();
19                         break;
20                     case "link":
21                         channel.Link = reader.ReadString();
22                         break;
23                     case "description":
24                         channel.Description = reader.ReadString();
25                         break;
26                     case "content":
27                         channel.Content = reader.ReadString();
28                         break;
29                     case "pubDate":
30                         channel.PubDate = reader.ReadString();
31                         break;
32                     case "author":
33                         channel.Author = reader.ReadString();
34                         break;
35                     case "category":
36                         channel.Category = reader.ReadString();
37                         break;
38                     default:
39                         break;
40                 }
41             }
42         }
43     }
44     return lstChannel;
45 }

　　四、Linq to XML 方式

代码

1 static IList testXmlLinq()
 2 {
 3     var xd = XDocument.Load(xmlStream);
 4     var list = from node in xd.Elements("channel").Descendants("item")
 5                 select new
 6                 {
 7                     Title = node.Element("title").Value,
 8                     Link = node.Element("link").Value,
 9                     Description = node.Element("description").Value,
10                     Content = node.Element("content").Value,
11                     PubDate = node.Element("pubDate").Value,
12                     Author = node.Element("author").Value,
13                     Category = node.Element("category").Value
14                 };
15     return list.ToList();
16 }

　　测试结果：

XmlDocment    47ms    
XPathNavigator    42ms    
XmlTextReader    23ms    
Xml Linq    28ms

　　小结一下自己的认识，XmlDocument的操作基本按W3C的DOM操作方式，不过要将全部节点解析成对象加载到内存中，往往造成很大浪费。所以微软自己的编程规范也不推荐用它。这里由于读取了所有节点，可能因此性能和Navigator方式相差不大。在三种随机读取方式中，Xml Linq性能最高，只是方法名有点别扭。XmlTextReader方式是所谓的SAX，只读向前，无疑性能最高，不过实现上麻烦了不少，要比较精确的控制访问逻辑，也无法用匿名类存储数据。

　　.Net 3.5发布Xml Linq可以很好地取代前两种方式，通常情况下，最好用它。只有个别场合，如果对性能要求极高，或者读取Xml数据量太大不能一下子下载或读取到内存中，那就只好痛苦委身于XmlTextReader了。

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