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 
   " 
   ) 
   %>' />