Imports System.Data
Imports System.Data.OleDb
Public Class relation
Inherits System.Web.UI.Page#Region " Web 窗体设计器生成的代码 " '该调用是 Web 窗体设计器所必需的。
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent() End Sub
Protected WithEvents lbllist As System.Web.UI.WebControls.Label '注意: 以下占位符声明是 Web 窗体设计器所必需的。
'不要删除或移动它。
Private designerPlaceholderDeclaration As System.Object Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
'CODEGEN: 此方法调用是 Web 窗体设计器所必需的
'不要使用代码编辑器修改它。
InitializeComponent()
End Sub#End Region
Private connectionstring As String = "provider=sqloledb.1; data source=localhost; initial catalog=pubs; integrated security=sspi"
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'在此处放置初始化页的用户代码
If Me.IsPostBack = False Then
createlist()
End If
End Sub
Private Sub createlist()
Dim selectsql As String
selectsql = "select au_lname,au_fname,au_id from authors"
Dim con As New OleDbConnection(connectionstring)
Dim cmd As New OleDbCommand(selectsql, con)
Dim adapter As New OleDbDataAdapter(cmd)
Dim dspubs As New DataSet Try
con.Open()
adapter.Fill(dspubs, "authors")
cmd.CommandText = "select au_id,title_id from titleauthor"
adapter.Fill(dspubs, "titleauthor") cmd.CommandText = "select title_id,title from titles"
adapter.Fill(dspubs, "titles") Catch err As Exception
lbllist.text = "error reading list of names."
lbllist.text &= err.Message
Finally
If (Not con Is Nothing) Then
con.Close()
End If
End Try
Dim titles_titleauthor As DataRelation
Dim authors_titleauthor As DataRelation
titles_titleauthor = New DataRelation("", dspubs.Tables("titles").Columns("title_id"), dspubs.Tables("titleauthor").Columns("title_id"))
authors_titleauthor = New DataRelation("", dspubs.Tables("authors").Columns("au_id"), dspubs.Tables("titleauthor").Columns("au_id")) dspubs.relations.add(titles_titleauthor)
dspubs.relations.add(authors_titleauthor) Dim rowauthor, rowtitleauthor, rowtitle As DataRow For Each rowauthor In dspubs.tables("authors").rows lbllist.Text &= "<br><b>" & rowauthor("au_fname")
lbllist.Text &= "" & rowauthor("au_lname") & "</b><br>"
For Each rowtitleauthor In rowauthor.GetChildRows(authors_titleauthor)
For Each rowtitle In rowtitleauthor.GetParentRows(titles_titleauthor)
lbllist.Text &= " "
lbllist.Text &= rowtitle("title") & "<br>" Next
Next
Next
End SubEnd Class行 57: Dim titles_titleauthor As DataRelation
行 58: Dim authors_titleauthor As DataRelation
行 59: titles_titleauthor = New DataRelation("", dspubs.Tables("titles").Columns("title_id"), dspubs.Tables("titleauthor").Columns("title_id"))
行 60: authors_titleauthor = New DataRelation("", dspubs.Tables("authors").Columns("au_id"), dspubs.Tables("titleauthor").Columns("au_id"))
行 61:
未将对象引用设置到对象的实例!高手帮我看看,谢谢!
Imports System.Data.OleDb
Public Class relation
Inherits System.Web.UI.Page#Region " Web 窗体设计器生成的代码 " '该调用是 Web 窗体设计器所必需的。
<System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent() End Sub
Protected WithEvents lbllist As System.Web.UI.WebControls.Label '注意: 以下占位符声明是 Web 窗体设计器所必需的。
'不要删除或移动它。
Private designerPlaceholderDeclaration As System.Object Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init
'CODEGEN: 此方法调用是 Web 窗体设计器所必需的
'不要使用代码编辑器修改它。
InitializeComponent()
End Sub#End Region
Private connectionstring As String = "provider=sqloledb.1; data source=localhost; initial catalog=pubs; integrated security=sspi"
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'在此处放置初始化页的用户代码
If Me.IsPostBack = False Then
createlist()
End If
End Sub
Private Sub createlist()
Dim selectsql As String
selectsql = "select au_lname,au_fname,au_id from authors"
Dim con As New OleDbConnection(connectionstring)
Dim cmd As New OleDbCommand(selectsql, con)
Dim adapter As New OleDbDataAdapter(cmd)
Dim dspubs As New DataSet Try
con.Open()
adapter.Fill(dspubs, "authors")
cmd.CommandText = "select au_id,title_id from titleauthor"
adapter.Fill(dspubs, "titleauthor") cmd.CommandText = "select title_id,title from titles"
adapter.Fill(dspubs, "titles") Catch err As Exception
lbllist.text = "error reading list of names."
lbllist.text &= err.Message
Finally
If (Not con Is Nothing) Then
con.Close()
End If
End Try
Dim titles_titleauthor As DataRelation
Dim authors_titleauthor As DataRelation
titles_titleauthor = New DataRelation("", dspubs.Tables("titles").Columns("title_id"), dspubs.Tables("titleauthor").Columns("title_id"))
authors_titleauthor = New DataRelation("", dspubs.Tables("authors").Columns("au_id"), dspubs.Tables("titleauthor").Columns("au_id")) dspubs.relations.add(titles_titleauthor)
dspubs.relations.add(authors_titleauthor) Dim rowauthor, rowtitleauthor, rowtitle As DataRow For Each rowauthor In dspubs.tables("authors").rows lbllist.Text &= "<br><b>" & rowauthor("au_fname")
lbllist.Text &= "" & rowauthor("au_lname") & "</b><br>"
For Each rowtitleauthor In rowauthor.GetChildRows(authors_titleauthor)
For Each rowtitle In rowtitleauthor.GetParentRows(titles_titleauthor)
lbllist.Text &= " "
lbllist.Text &= rowtitle("title") & "<br>" Next
Next
Next
End SubEnd Class行 57: Dim titles_titleauthor As DataRelation
行 58: Dim authors_titleauthor As DataRelation
行 59: titles_titleauthor = New DataRelation("", dspubs.Tables("titles").Columns("title_id"), dspubs.Tables("titleauthor").Columns("title_id"))
行 60: authors_titleauthor = New DataRelation("", dspubs.Tables("authors").Columns("au_id"), dspubs.Tables("titleauthor").Columns("au_id"))
行 61:
未将对象引用设置到对象的实例!高手帮我看看,谢谢!
行 58: Dim authors_titleauthor As DataRelation
行 59: titles_titleauthor = New DataRelation("", dspubs.Tables("titles").Columns("title_id"), dspubs.Tables("titleauthor").Columns("title_id"))
行 60: authors_titleauthor = New DataRelation("", dspubs.Tables("authors").Columns("au_id"), dspubs.Tables("titleauthor").Columns("au_id"))
行 61: 这几行出错?貌似没问题啊 看看IDE停在哪
Dim authors_titleauthor As DataRelation = New DataRelation("", dspubs.Tables("authors").Columns("au_id"), dspubs.Tables("titleauthor").Columns("au_id"))改成这样