文章的上一篇和下一篇导航

当浏览文章时，希望在文章下面有一个导航，就是上一篇和下一篇的功能。可从下三张截图看到效果：

 

 

 

要SQL查询语句前，就须把上一篇和下一篇的文章ID找出来，下面的SQL语句有些字段已经省略。

 
   
    SELECT 
    [
    ArticleId
    ],
    [
    Subject
    ],
    
    (
    SELECT 
    MAX(
    [
    ArticleId
    ]) 
    FROM 
    [
    dbo
    ].
    [
    Article
    ] 
    AS a1 
    WHERE a1.
    [
    ArticleId
    ] 
    < a.
    [
    ArticleId
    ]) 
    AS 
    [
    PrevArticleId
    ],
    
    (
    SELECT 
    MIN(
    [
    ArticleId
    ]) 
    FROM 
    [
    dbo
    ].
    [
    Article
    ] 
    AS a1 
    WHERE a1.
    [
    ArticleId
    ] 
    > a.
    [
    ArticleId
    ]) 
    AS 
    [
    NextArticleId
    ]    
    
    
    FROM 
    [
    dbo
    ].
    [
    Article
    ] 
    AS a
   
  

 

执行结果：

 

数据库方面完成了，接下来在asp.net实现，可以首先创建一个用户控件：

ArticleNavigation.ascx：

 
   
    <%
    @ Control Language
    =
    "
    VB
    "
     AutoEventWireup
    =
    "
    false
    "
     CodeFile
    =
    "
    ArticleNavigation.ascx.vb
    "
     Inherits
    =
    "
    SiteControls_ArticleNavigation
    "
     
    %>
    
上一篇：
    <
    asp:HyperLink 
    ID
    ="HyperLinkPrev"
     runat
    ="server"
     Target
    ="_blank"
    ></
    asp:HyperLink
    > 
    <
    br 
    />
    
下一篇：
    <
    asp:HyperLink 
    ID
    ="HyperLinkNext"
     runat
    ="server"
     Target
    ="_blank"
    ></
    asp:HyperLink
    >
   
  

 

ArticleNavigation.ascx.vb：

 
   
    Imports System.Data
    

    Imports Insus.NET
    

    

    Partial 
    Class SiteControls_ArticleNavigation
    
    
    Inherits System.Web.UI.UserControl
    
    
    Dim objArticle 
    As 
    New Article()
    

    
    
    Private _PrevArticleId 
    As 
    String
    
    
    Private _NextArticleId 
    As 
    String
    

    
    
    Public 
    WriteOnly 
    Property PrevArticleId 
    As 
    String
    
        
    Set(value 
    As 
    String)
    
            _PrevArticleId = value
    
        
    End 
    Set
    
    
    End Property
    

    
    
    Public 
    WriteOnly 
    Property NextArticleId 
    As 
    String
    
        
    Set(value 
    As 
    String)
    
            _NextArticleId = value
    
        
    End 
    Set
    
    
    End Property
    

    
    
    Protected 
    Sub Page_Load(sender 
    As 
    Object, e 
    As EventArgs) 
    Handles 
    Me.Load
    
        Data_Binding()
    
    
    End Sub
    

    
    
    Private 
    Sub Data_Binding()
    
        
    If 
    String.IsNullOrEmpty(_PrevArticleId) 
    Then
    
            
    Me.HyperLinkPrev.Text = 
    "
    无
    "
    
        
    Else
    
            
    Dim objPrevDataRow 
    As DataRow = objArticle.GetArticleByPrimaryKey(_PrevArticleId).Rows(
    0)
    
            
    Me.HyperLinkPrev.Text = objPrevDataRow(
    "
    Subject
    ")
    
            
    Me.HyperLinkPrev.NavigateUrl = 
    "
    ~/ArticleView.aspx?ID=
    " & _PrevArticleId
    
        
    End 
    If
    

    
        
    If 
    String.IsNullOrEmpty(_NextArticleId) 
    Then
    
            
    Me.HyperLinkNext.Text = 
    "
    无
    "
    
        
    Else
    
            
    Dim objNextDataRow 
    As DataRow = objArticle.GetArticleByPrimaryKey(_NextArticleId).Rows(
    0)
    
            
    Me.HyperLinkNext.Text = objNextDataRow(
    "
    Subject
    ")
    
            
    Me.HyperLinkNext.NavigateUrl = 
    "
    ~/ArticleView.aspx?ID=
    " & _NextArticleId
    
        
    End 
    If
    
    
    End Sub
    

    

    End Class
   
  

 

在文章浏览的aspx中，用户控控件需要传入前一篇的文章ID和下一篇的文章ID，下面的PrevArticleId和NextArticleId两个都是用户控件的public的属性。 

 
   
     
    <
    uc1:ArticleNavigation 
    ID
    ="ArticleNavigation1"
     runat
    ="server"
     PrevArticleId
    ='<%# 
    Eval("PrevArticleId")%
    >'
    
                NextArticleId='
    <%
    # 
    Eval
    (
    "
    NextArticleId
    "
    )
    %>' />