幾個月來,疑被SOA,一直在和xml操作打交道,SQL差不多又忘光了.現在已經知道,至少有四種常用人XML數據操作方式(好像java差不多),不過還沒有實際比較過這些方式各有哪些特點或優劣.正好看到網上也沒有這方面的實驗,偶來總結一下.
測試開始先讀取XML源,用一個比較大的rss文件鏈接,複製到項目bin/debug目錄下.
Stream xmlStream = new MemoryStream(File.ReadAllBytes(path)); 一、XmlDocument 方式
代碼
static IList testXmlDocument()
{
var doc = new XmlDocument();
doc.Load(xmlStream);
var nodeList = doc.DocumentElement.ChildNodes;
var lstChannel = new List<Object>(nodeList.Count );
foreach (XmlNode node in nodeList)
{
var channel = new { Title = node.SelectSingleNode("title").
InnerText, Link = node.SelectSingleNode("link").
InnerText, Description = node.SelectSingleNode("description").
InnerText, Content = node.SelectSingleNode("content").
InnerText, PubDate = node.SelectSingleNode("pubDate").
InnerText, Author = node.SelectSingleNode("author").
InnerText, Category = node.SelectSingleNode("category").
InnerText };
lstChannel.Add(channel);
}
return lstChannel;
}
二、XPathNavigator 方式
代碼
static IList testXmlNavigator()
{
var doc = new XmlDocument();
doc.Load(xmlStream);
var nav = doc.CreateNavigator();
nav.MoveToRoot();
var nodeList = nav.Select("/channel/item");
var lstChannel = new List<Object>(nodeList.Count);
foreach (XPathNavigator node in nodeList)
{
var channel = new {
Title = node.SelectSingleNode("title").
Value, Link = node.SelectSingleNode("link").
Value, Description = node.SelectSingleNode("description").
Value, Content = node.SelectSingleNode("content").
Value, PubDate = node.SelectSingleNode("pubDate").
Value, Author = node.SelectSingleNode("author").
Value, Category = node.SelectSingleNode("category").
Value };
lstChannel.Add(channel);
}
return lstChannel;
}
三、XmlTextReader 方式
代碼
static List<Channel> testXmlReader()
{
var lstChannel = new List<Channel>();
var reader = XmlReader.Create(xmlStream);
while (reader.Read())
{
if
(reader.Name == "item" && reader.NodeType == XmlNodeType.Element)
{ var channel = new Channel();
lstChannel.Add(channel);
while (reader.Read())
{
if (reader.Name == "item") break;
if (reader.NodeType != XmlNodeType.Element) continue;
switch (reader.Name)
{
case "title": channel.Title = reader.ReadString();
break;
case "link": channel.Link = reader.ReadString();
break;
case "description": channel.Description = reader.ReadString();
break;
case "content": channel.Content = reader.ReadString();
break;
case "pubDate": channel.PubDate = reader.ReadString();
break;
case "author": channel.Author = reader.ReadString();
break;
case "category": channel.Category = reader.ReadString();
break;
default: break;
}}}}
return lstChannel;
}
四、Linq to XML 方式
代碼
static IList testXmlLinq()
{
var xd = XDocument.Load(xmlStream);
var list = from node in xd.Elements("channel").Descendants("item")
select new
{
Title = node.Element("title").
Value, Link = node.Element("link").
Value, Description = node.Element("description").
Value, Content = node.Element("content").
Value, PubDate = node.Element("pubDate").
Value, Author = node.Element("author").
Value, Category = node.Element("category").
Value };
return list.ToList();
測試結果:
XmlDocment 47ms
XPathNavigator 42ms
XmlTextReader 23ms
Xml Linq 28ms
小結一下自己的認識,XmlDocument的操作基本按W3C的DOM操作方式,不過要將全部節點解析成對象載入到內存中,往往造成很大浪費.所以微軟自己的編程規範也不推薦用它.這裡由於讀取了所有節點,可能因此性能和Navigator方式相差不大.在三種隨機讀取方式中,Xml Linq性能最高,只是方法名有點彆扭.XmlTextReader方式是所謂的SAX,只讀向前,無疑性能最高,不過實現上麻煩了不少,要比較精確的控制訪問邏輯,也無法用匿名類存儲數據.
.Net 3.5發布Xml Linq可以很好地取代前兩種方式,通常情況下,最好用它.只有個別場合,如果對性能要求極高,或者讀取Xml數據量太大不能一下子下載或讀取到內存中,那就只好痛苦委身於XmlTextReader了.
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