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")%>' />