ASP.Net 2.0+AJAX+Orcas构建简易的RSS新闻阅读器

本程序参考了《ASP.NET Ajax程序设计—第I卷》“9.4 DynamicPopulate：“穷人的”UpdatePanel” 里面的一些框架

 下面是我的代码清单：

MySelf/RssNews.aspx	前台页面
MySelf/RssNews.css	样式表
MySelf/NewsService.asmx	用于内容显示的Web Service
Images/ajax-loader.gif	异步刷新时的图标
App_Code/NewsData.dbml	新闻数据的实体类
App_Code/NewsDataService.vb	数据提供器
App_Code/NewsService.vb	Web Service的后端文件

主要内容：

App_Code/NewsData.dbml:

App_Code/NewsDataService.vb:

Imports  Microsoft.VisualBasic
Imports  System.Collections.Generic
Imports  System.Xml
Imports  System.Net

Public   Class NewsDataService Class NewsDataService
    ''' <summary>
    ''' 存放数据的静态对象
    ''' </summary>
    ''' <remarks></remarks>
    Shared m_data As List(Of NewsEntry)
    ''' <summary>
    ''' 用于存放RSSFeedUrl
    ''' </summary>
    ''' <remarks></remarks>
    Private Const feedUrl As String = "http://blog.youkuaiyun.com/lishewen/Rss.aspx"

    ''' <summary>
    ''' 获取文章的简要列表
    ''' </summary>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function GetNewsList()Function GetNewsList() As List(Of NewsEntryLight)
        If m_data Is Nothing Then
            initData()
        End If
        Return m_data.ConvertAll(Of NewsEntryLight)(AddressOf NewsEntryToNewsEntryLight)
    End Function

    ''' <summary>
    ''' 实现一个从NewsEntry到NewsEntryLight的Converter
    ''' </summary>
    ''' <param name="NE"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Private Shared Function NewsEntryToNewsEntryLight()Function NewsEntryToNewsEntryLight(ByVal NE As NewsEntry) As NewsEntryLight
        Return NE
    End Function

    ''' <summary>
    ''' 从Rss源里获取数据初始化
    ''' </summary>
    ''' <remarks></remarks>
    Private Shared Sub initData()Sub initData()
        m_data = New List(Of NewsEntry)
        Dim rssReader As XmlTextReader = Nothing
        Dim itemCount = 0
        Try
            Dim rssFeed = WebRequest.Create(feedUrl)
            rssReader = New XmlTextReader(rssFeed.GetResponse.GetResponseStream)
            While rssReader.Read
                If rssReader.IsStartElement And rssReader.LocalName = "item" Then
                    Dim itemReader As XmlReader = Nothing
                    Try
                        Dim NewsItem As New NewsEntry
                        NewsItem.ID = itemCount
                        NewsItem.Views = 0
                        itemReader = rssReader.ReadSubtree
                        While itemReader.Read
                            If itemReader.IsStartElement Then
                                Select Case itemReader.LocalName
                                    Case "title"
                                        NewsItem.Title = itemReader.ReadString
                                    Case "pubDate"
                                        NewsItem.PostDate = Date.Parse(itemReader.ReadString)
                                    Case "description"
                                        NewsItem.Content = itemReader.ReadString
                                    Case "creator"
                                        NewsItem.Author = itemReader.ReadString
                                End Select
                            End If
                        End While
                        m_data.Add(NewsItem)
                        itemCount += 1
                    Catch ex As Exception

                    Finally
                        If Not itemReader Is Nothing Then
                            itemReader.Close()
                        End If
                    End Try
                End If
                '获取新闻数为10条记录
                If itemCount >= 10 Then
                    Exit While
                End If
            End While
        Catch ex As Exception

        Finally
            If Not rssReader Is Nothing Then
                rssReader.Close()
            End If
        End Try
    End Sub

    ''' <summary>
    ''' 获得新闻的详细数据
    ''' </summary>
    ''' <param name="id">新闻ID</param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Shared Function GetNewsDetail()Function GetNewsDetail(ByVal id As Integer) As NewsEntry
        If m_data Is Nothing Then
            initData()
        End If
        '用VB9新增的XX表达式来筛选数据
        Dim news = From NewsItem In m_data Where NewsItem.ID = id Select NewsItem
        news(0).Views += 1
        Return news(0)
    End Function
End Class

App_Code/NewsService.vb:

Imports  System.Web
Imports  System.Web.Services
Imports  System.Web.Services.Protocols

< WebService( Namespace : = " http://www.lishewen.com/ " ) >  _
< WebServiceBinding(ConformsTo: = WsiProfiles.BasicProfile1_1) >  _
< Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated() >  _
< Script.Services.ScriptService() >  _
Public   Class  NewsService
     Inherits  System.Web.Services.WebService

     ' '' <summary>
     ' '' 获取新闻详细信息的HTML
     ' '' </summary>
     ' '' <param name="contextKey"></param>
     ' '' <returns></returns>
     ' '' <remarks></remarks>
     < WebMethod() >  _
     Public   Function  GetNewsDetailsHTMLString( ByVal  contextKey  As   String )  As   String
         Dim  newsId  As   Integer
         If   Not   Integer .TryParse(contextKey, newsId)  Then
             Return   String .Empty
         End   If
         Dim  news  =  NewsDataService.GetNewsDetail(newsId)
         Dim  newsHTMLBuilder  As   New  System.Text.StringBuilder
        newsHTMLBuilder.AppendFormat( " <div style='text-align:center;'>posted by {0} at {1},{2} views</div> " , news.Author, news.PostDate.ToShortDateString, news.Views)
        newsHTMLBuilder.AppendFormat( " <div>{0}</div> " , news.Content)
         Return  newsHTMLBuilder.ToString
     End Function

End Class

MySelf/RssNews.css:

body  {...} {
}
.updating
{...} {
    background-image:url('../Images/ajax-loader.gif');
    background-repeat:no-repeat;
    padding:2px;
    height:2em;
    margin:5px;
}

MySelf/RssNews.aspx:

< %@ Page  Language ="VB"  AutoEventWireup ="false"  CodeFile ="RssNews.aspx.vb"  Inherits ="MySelf_RssNews"  % >

<! 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 > Untitled Page </ title >
     < link  href ="RssNews.css"  rel ="stylesheet"  type ="text/css"   />

     < script  type ="text/javascript" >
    
      function pageLoad() {
      }
    
     </ script >

</ head >
< body >
     < form  id ="form1"  runat ="server" >
     < div >
         < asp:ScriptManager  ID ="ScriptManager1"  runat ="server"   />
         < asp:ObjectDataSource  ID ="NewsDataSource"  runat ="server"  SelectMethod ="GetNewsList"
            TypeName ="NewsDataService" ></ asp:ObjectDataSource >
         < asp:GridView  ID ="GridView1"  runat ="server"  AutoGenerateColumns ="False"  DataSourceID ="NewsDataSource"
            ShowHeader ="False" >
             < Columns >
                 < asp:TemplateField >
                     < ItemTemplate >
                         < a  name ='<%#  Eval("ID","name{0}") % > '> </ a >
                         < asp:HyperLink  ID ="hlMore"  runat ="server"  NavigateUrl ='<%#  Eval("ID", "#name{0}") % > '>more... </ asp:HyperLink >
                         < asp:Label  ID ="lbTitle"  runat ="server"  Font-Bold ="True"  Text ='<%#  Bind("Title") % > '> </ asp:Label >
                         < asp:Panel  ID ="newsDetails"  runat ="server" >
                         </ asp:Panel >
                         < asp:DynamicPopulateExtender  ID ="DynamicPopulateExtender1"  runat ="server"  ContextKey ='<%#  Eval("ID") % > '
                            Enabled="True" PopulateTriggerControlID="hlMore" TargetControlID="newsDetails"
                            UpdatingCssClass="updating" ServicePath="~/MySelf/NewsService.asmx" ServiceMethod="GetNewsDetailsHTMLString">
                         </ asp:DynamicPopulateExtender >
                     </ ItemTemplate >
                     < ItemStyle  CssClass ="gridRow"   />
                 </ asp:TemplateField >
             </ Columns >
         </ asp:GridView >
     </ div >
     </ form >
</ body >
</ html >