Sv: Codebehind och "Object variable or With block variable not set"

Codebehind och "Object variable or With block variable not set"

Postades av 2003-09-02 16:01:25 - Martin Söderlund, i forum asp.net generellt, Tråden har 4 Kommentarer och lästs av 797 personer

Jag håller på att göra en sajt där informationen som visas baseras på vilken info som tas emot från default.aspx?category=xxx&subcat=xxx och har nu stött på ett fel i samband med codebehind.

Så här ser min codebehindsida ut:
news.aspx.vb

Imports System.Web
Imports System.Web.UI
Imports System.Web.UI.Page
Imports System.Web.UI.Control
Imports System.Data
Imports System.Data.OleDb

Public Class PL : Inherits Page

Sub Page_Load
Dim tbl_news As object

Dim Cn As New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" & Server.MapPath("dbms\db_news.mdb"))
Dim SQL As string = "SELECT n_name,n_news,n_date FROM tbl_news"

Dim Cm As New OleDbCommand(SQL,Cn)
Dim dbRead As OleDbDataReader

Dim Container As object
Cn.Open()
dbRead = Cm.ExecuteReader()

tbl_news.DataSource = dbRead '<--- det är där felet ligger!!
tbl_news.DataBind()

dbRead.Close()
Cn.Close()
End Sub

End Class

Sidan som klassen och infon från databasen ska visas på heter main.aspx och ser ut så här:

<% Page Language="VB" Strict="False" Debug="True" inherits="PL" src="behind/news.aspx.vb" %>

<span class="head">Startsidan</span>

<form id="news" runat="server">
<asp:repeater id="tbl_news" runat="server">
<ItemTemplate><%# Container.DataItem("n_date") %><br />
<%# Container.DataItem("n_news") %><br />
<%# Container.DataItem("n_name") %><br /><br /></ItemTemplate>
</asp:repeater>

</form>

Slutligen har vi sidan default.aspx, där, beroende på info i subcat-querystringen, exekveras en sida. Så här ser default.aspx ut:

<% Page Language="VB" Strict="True" Debug="True" %>
<%
Dim cat As string = Request.Querystring("category")
Dim subcat As string = Request.Querystring("subcat")
%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>Predictive Sales</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<link href="style.css" type="text/css" rel="stylesheet" />
</head>

<body>

<table cellspacing="1" cellpadding="2" border="0">
<tbody>
<tr>
<td><img alt="Predictive Sales" src="gfx/logo.gif" border="0" /></td>
</tr>
<tr>
<td>

<table cellspacing="0" cellpadding="0" border="0">
<tbody>
<tr>
<td valign="top">



</td>
<td width="5"></td>
<td valign="top" width="600">
<%
Select Case subcat

Case ""
Server.Execute("main.aspx")

Case "main"
Server.Execute("main.aspx")

Case "company"
Server.Execute("about/aboutcompany.aspx")

Case "companyculture"
Server.Execute("about/companyculture.aspx")

Case "management"
Server.Execute("about/management.aspx")

Case "vdspeaks"
Server.Execute("about/vdspeaks.aspx")

Case "aboutservices"
Server.Execute("services/aboutservices.aspx")

Case "fieldsales"
Server.Execute("services/fieldsales.aspx")

Case "telesales"
Server.Execute("services/telesales.aspx")

Case "telemarketing"
Server.Execute("services/telemarketing.aspx")

Case "salesconsulting"
Server.Execute("services/salesconsulting.aspx")

Case "abouttechnology"
Server.Execute("tech/abouttechnology.aspx")

Case "predictivedialer"
Server.Execute("tech/predictivedialer.aspx")

Case "telestarcms"
Server.Execute("tech/telestarcms.aspx")

Case "aboutcustomers"
Server.Execute("customers/aboutcustomers.aspx")

Case "canaldigital"
Server.Execute("customers/canaldigital.aspx")

Case "foraldranatet"
Server.Execute("customers/foraldranatet.aspx")

Case "ap-fastigheter"
Server.Execute("customers/ap-fastigheter.aspx")

Case "monster"
Server.Execute("customers/monster.aspx")

Case "staffphilosophy"
Server.Execute("recruitment/staffphilosophy.aspx")

Case "workforus"
Server.Execute("recruitment/workforus.aspx")

Case "unoccupiedjobs"
Server.Execute("recruitment/unoccupiedjobs.aspx")

Case "contact"
Server.Execute("contact.aspx")

Case Else
Server.Execute("404.aspx")

End Select
%>
</td>
</tr>
</tbody>
</table>

</td>
</tr>
</tbody>
</table>

</body>
</html>

Nu är det så att jag får följande problem när jag kör default.aspx?category=main&subcat=main och alltså exekverar main.aspx och den sidans codebehind-sida. Följande felmeddelande genereras:

Object variable or With block variable not set.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object variable or With block variable not set.

Source Error:

Line 24: dbRead = Cm.ExecuteReader()
Line 25:
Line 26: tbl_news.DataSource = dbRead
Line 27: tbl_news.DataBind()
Line 28:

Source File: e:\web\pred\behind\news.aspx.vb Line: 26

Stack Trace:

[NullReferenceException: Object variable or With block variable not set.]
Microsoft.VisualBasic.CompilerServices.LateBinding.InternalLateSet(Object o, Type& objType, String name, Object[] args, String[] paramnames, Boolean OptimisticSet, CallType UseCallType) +1994
Microsoft.VisualBasic.CompilerServices.LateBinding.LateSet(Object o, Type objType, String name, Object[] args, String[] paramnames) +28
PL.Page_Load() in e:\web\pred\behind\news.aspx.vb:26
System.Web.Util.ArglessEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +10
System.Web.UI.Control.OnLoad(EventArgs e) +67
System.Web.UI.Control.LoadRecursive() +35
System.Web.UI.Page.ProcessRequestMain() +731

Felet ligger alltså på rad 26 och härrör till tbl_news.DataSource = dbRead.

Nu undrar jag vad problemet är, samt hur man löser det. MYCKET tacksam för hjälp. :D

Svara