XmlReader 讀取器讀取內存流 MemoryStream 的注意事項

MemoryStream對象提供了無需進行IO就可以創建Stream的方法,XmlTextWriter和XmlReader提供快速書寫和讀取XML內容的方法,結合MemoryStream,就可以直接在內存中構造XmlTextWriter,並用XmlReader進行讀取。

使用MemoryStream和XmlTextWriter進行書寫XML,需要注意兩點:XmlTextWriter.Flush操作和重設MemoryStream.Position = 0。

C# 

<%@ Page Language="C#"%>
<%@ Import Namespace="System.Xml" %>
<%@ Import Namespace="System.IO" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
  protected 
void Button1_Click(object sender, EventArgs e)
  {
    Response.Clear();
    Response.ContentType 
= "text/xml";
    MemoryStream msXml 
= new MemoryStream();
    XmlTextWriter xmlWriter 
= new XmlTextWriter(msXml, Encoding.UTF8);
    xmlWriter.WriteStartElement(
"rss");
    xmlWriter.WriteAttributeString(
"version""2.0");
    xmlWriter.WriteStartElement(
"channel");
    xmlWriter.WriteElementString(
"title""【孟憲會之精彩世界】");
    xmlWriter.WriteElementString(
"link""http://dotnet.aspx.cc/Rss.aspx");
    xmlWriter.WriteElementString(
"description""NET開發技術。");
    xmlWriter.WriteElementString(
"language""zh-CN");
    xmlWriter.WriteElementString(
"copyright""Copyright 1999-2007【孟憲會之精彩世界】");
    xmlWriter.WriteElementString(
"managingEditor""amxh[AT]21cn.com");
    xmlWriter.WriteStartElement(
"image");
    xmlWriter.WriteElementString(
"title""【孟憲會之精彩世界】");
    xmlWriter.WriteElementString(
"width""144");
    xmlWriter.WriteElementString(
"height""35");
    xmlWriter.WriteElementString(
"link""http://dotnet.aspx.cc/");
    xmlWriter.WriteElementString(
"url""http://dotnet.aspx.cc/Images/LogoRss.gif");
    xmlWriter.WriteEndElement();

    
//循環讀出數據庫內容列表,忽略
    //while (objReader.Read())
    //{
    //  xmlWriter.WriteStartElement("item");
    //  xmlWriter.WriteElementString("title", objReader.GetString(0));
    //  xmlWriter.WriteElementString("description", objReader.GetString(1));
    //  xmlWriter.WriteElementString("link", "http://dotnet.aspx.cc/article/a933b187-06c3-4263-9eec-414a54d9c815/read.aspx");
    //  xmlWriter.WriteElementString("pubDate", objReader.GetDateTime(3).ToString("G"));
    //  xmlWriter.WriteEndElement();
    //}
    //objReader.Close();
    xmlWriter.WriteStartElement("item");
    xmlWriter.WriteElementString(
"title""ASP.NET 2.0中直接將Access數據庫導入到Excel文件中");
    xmlWriter.WriteElementString(
"description""ASP.NET 2.0中直接將Access數據庫導入到Excel文件中");
    xmlWriter.WriteElementString(
"link""http://dotnet.aspx.cc/article/a933b187-06c3-4263-9eec-414a54d9c815/read.aspx");
    xmlWriter.WriteElementString(
"pubDate""Sat, 02 Dec 2006 09:39:58 GMT");
    xmlWriter.WriteEndElement();
    xmlWriter.WriteEndElement();
    xmlWriter.WriteEndElement();
    xmlWriter.Flush();  
// 確保書寫器更新到Stream中;
    msXml.Position = 0// 重置流的位置,以便我們可以從頭讀取     
    XmlReader xmlReader = XmlReader.Create(msXml);
    
while (xmlReader.Read())
    {
      
if (xmlReader.Name == "rss")
      {
        Response.Write(xmlReader.ReadOuterXml());
      }
    }
    Response.End();
    msXml.Close();
    xmlWriter.Close();
    xmlReader.Close();
  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
  
<title>XmlReader 讀取器讀取內存流 MemoryStream 的注意事項</title>
</head>
<body>
  
<form id="form1" runat="server">
    
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="讀取數據" />
  
</form>
</body>
</html>

VB.NET

Protected Sub Button1_Click(ByVal sender As ObjectByVal e As EventArgs) 
 Response.Clear 
 Response.ContentType 
= "text/xml" 
 
Dim msXml As MemoryStream = New MemoryStream 
 
Dim xmlWriter As XmlTextWriter = New XmlTextWriter(msXml, Encoding.UTF8) 
 xmlWriter.WriteStartElement(
"rss"
 xmlWriter.WriteAttributeString(
"version""2.0"
 xmlWriter.WriteStartElement(
"channel"
 xmlWriter.WriteElementString(
"title""【孟憲會之精彩世界】"
 xmlWriter.WriteElementString(
"link""http://dotnet.aspx.cc/Rss.aspx"
 xmlWriter.WriteElementString(
"description""NET開發技術。"
 xmlWriter.WriteElementString(
"language""zh-CN"
 xmlWriter.WriteElementString(
"copyright""Copyright 1999-2007【孟憲會之精彩世界】"
 xmlWriter.WriteElementString(
"managingEditor""amxh[AT]21cn.com"
 xmlWriter.WriteStartElement(
"image"
 xmlWriter.WriteElementString(
"title""【孟憲會之精彩世界】"
 xmlWriter.WriteElementString(
"width""144"
 xmlWriter.WriteElementString(
"height""35"
 xmlWriter.WriteElementString(
"link""http://dotnet.aspx.cc/"
 xmlWriter.WriteElementString(
"url""http://dotnet.aspx.cc/Images/LogoRss.gif"
 xmlWriter.WriteEndElement 
 xmlWriter.WriteStartElement(
"item"
 xmlWriter.WriteElementString(
"title""ASP.NET 2.0中直接將Access數據庫導入到Excel文件中"
 xmlWriter.WriteElementString(
"description""ASP.NET 2.0中直接將Access數據庫導入到Excel文件中"
 xmlWriter.WriteElementString(
"link""http://dotnet.aspx.cc/article/a933b187-06c3-4263-9eec-414a54d9c815/read.aspx"
 xmlWriter.WriteElementString(
"pubDate""Sat, 02 Dec 2006 09:39:58 GMT"
 xmlWriter.WriteEndElement 
 xmlWriter.WriteEndElement 
 xmlWriter.WriteEndElement 
 xmlWriter.Flush 
 msXml.Position 
= 0 
 
Dim xmlReader As XmlReader = XmlReader.Create(msXml) 
 
While xmlReader.Read 
   
If xmlReader.Name = "rss" Then 
     Response.Write(xmlReader.ReadOuterXml) 
   
End If 
 
End While 
 Response.End 
 msXml.Close 
 xmlWriter.Close 
 xmlReader.Close 
End Sub



 
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