xpath 随笔

    由XmlDocument 对象创建的XPathNavigator 对象是可编辑的， 由XPathDocument 对象创建的XPathNavigator 对象是只读的。XPathNavigator 的 CanEdit 属性让您判断。 

    XPathDocument 对 XPath 和 XSLT 中的使用进行了优化，而且是只读模式，并且还可以在对xml文档运行XPath或者对内存中的xml运行XSLT的时候提供更好的性能。这些情况下，XPathDocument 应该在 XmlDocument之前优先考虑，只有在转换之前需要更新xml文档的时候才考虑使用XmlDocument.

xml格式的数据源有在前台有两种绑定形式，一种是<# XPath("key")> ，另一种是<%# XPathSelect("key") %>
下面举例说明：

<% @ Page Language = " C# "   %>
<% @ Import Namespace = " System.Xml "   %>
< script runat = " server " >
   private  XmlDataDocument xd  =   new  XmlDataDocument();
   protected   void  Page_Load( object  sender, EventArgs e)
   {
    xd.Load(Server.MapPath("XmlData.xml"));
    Repeater1.DataSource = xd.SelectNodes("//site");
    Repeater1.DataBind();
  }
</ script >
< html xmlns = " http://www.w3.org/1999/xhtml " >
< head runat = " server " >
   < title > XPath 方法绑定 </ title >
</ head >
< body >
   < form id = " form1 "  runat = " server " >
     < asp:Repeater ID = " Repeater1 "  runat = " server " >
       < ItemTemplate >
         < a href = " <%#XPath( " url " ) %> "  title = " <%#XPath( " name " )%> " >
           <% #XPath( " img " )  ==   null   ?  XPath( " name " ) :  " <img src=' "   +  XPath( " img " )  +   " ' style='border:0px'> " %>
         </ a >
         < br  />
         < br  />
       </ ItemTemplate >
     </ asp:Repeater >
   </ form >
</ body >
</ html >

<? xml version="1.0" encoding="utf-8"  ?>
< sites >
   < site >
     < name > .NET 开发者园地 </ name >
     < url > http://dotnet.aspx.cc/ </ url >
     < img > ../images/logo.gif </ img >
   </ site >
   < site >
     < name > .NET 技术交流社区 </ name >
     < url > http://community.csdn.net/ </ url >
     < img > ../images/logo_csdn.gif </ img >
   </ site >
   < site >
     < name > 播客站点 </ name >
     < url > http://blog.csdn.ent/net_lover/ </ url >
   </ site >
</ sites >

<% @ Page Language = " C# " %>

<! DOCTYPE html PUBLIC  " -//W3C//DTD XHTML 1.0 Transitional//EN "   " http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd " >

< html xmlns = " http://www.w3.org/1999/xhtml "   >
< head runat = " server " >
     < title > TemplateControl XPath and XPathSelect Example </ title >
</ head >
< body >
     < h3 > TemplateControl XPath Example </ h3 >
     < form id = " form1 "  runat = " server " >
     < div >
       < asp:XmlDataSource
        id = " XmlDataSource1 "  
        runat = " server "
        XPath = " contacts "  
        DataFile = " contacts.xml "   />     
       < asp:FormView 
        id = " FormView1 "  
        runat = " server "  
        DataSourceID = " XmlDataSource1 " >
         < ItemTemplate >
           < hr  />
           < asp:Repeater 
            id = " Repeater1 "  
            runat = " server "  
            DataSource = ' <%# XPathSelect("contact") %> '   >
             < ItemTemplate >
              Name:  <% # XPath( " name " )  %>   < br  />
              Note:  <% # XPath( " note " )  %>   < br  />
               < hr  />
             </ ItemTemplate >
           </ asp:Repeater >
         </ ItemTemplate >
       </ asp:FormView >
     </ div >
     </ form >
</ body >
</ html >

< contacts >
    < contact  id ="1" >
      < name > contact name 1 </ name >
      < note > contact note 1 </ note >
    </ contact >
    < contact  id ="2" >
      < name > contact name 2 </ name >
      < note > contact note 2 </ note >
    </ contact >
</ contacts >