###异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。

[sharplee82]

Imports System.Data.OleDb
Public Class MainForm
Inherits System.Web.UI.Page
Dim conn As OleDbConnection
Dim ds As New DataSet
Dim da As OleDbDataAdapter
Public dataView1 As DataView

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 Not IsPostBack Then
conn = New OleDbConnection(Application("conn"))
da = New OleDbDataAdapter

Dim delstring As String = "DELETE FROM Questions WHERE (Q_ID = @Original_Q_ID) "
delstring = delstring & "AND (BigClass_ID = @Original_BigClass_ID OR @Original_BigClass_ID IS NULL AND BigClass_ID IS NULL) "
delstring = delstring & "AND (HiteCounter = @Original_HiteCounter OR @Original_HiteCounter IS NULL AND HiteCounter IS NULL) AND "
delstring = delstring & "(ImageName = @Original_ImageName OR @Original_ImageName IS NULL AND ImageName IS NULL) AND "
delstring = delstring & " (Q_Note = @Original_Q_Note OR @Original_Q_Note IS NULL AND Q_Note IS NULL) AND (ReferTime = @Original_ReferTime OR "
delstring = delstring & "@Original_ReferTime IS NULL AND ReferTime IS NULL) AND (ReleaseTime = @Original_ReleaseTime OR "
delstring = delstring & "@Original_ReleaseTime IS NULL AND ReleaseTime IS NULL) AND (SmallClass_ID = @Original_SmallClass_ID OR "
delstring = delstring & "@Original_SmallClass_ID IS NULL AND SmallClass_ID IS NULL) AND (author = @Original_author OR @Original_author IS"
delstring = delstring & " NULL AND author IS NULL)"
'删除命令
da.DeleteCommand.CommandText = delstring
上面一句有错：异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实例。

[sharplee82]

堆栈跟踪:


[NullReferenceException: 未将对象引用设置到对象的实例。]
SharpLeeDiscussion.MainForm.Page_Load(Object sender, EventArgs e) in D:\公司网站\SharpLeeDiscussion\MainForm.aspx.vb:47
System.Web.UI.Control.OnLoad(EventArgs e)
System.Web.UI.Control.LoadRecursive()
System.Web.UI.Page.ProcessRequestMain()

[sharplee82]

还有一问题：: )刚想到.
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="data" value="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=DbUsed.mdb"></add>
</appSettings>
Source=？这里如何写，使DbUsed.mdb文件是当前应用程序下的数据库文件？

[qiuji]

这样写：
<add key="data" value="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=DbUsed.mdb"></add>
改成：
<add key="data" value="DbUsed.mdb"></add>

然后，
Imports System.Configuration
conn=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source="&Server.MapPath(ConfigurationSettings.AppSettings("ds")))

[qiuji]

不好意思，写错了：
conn=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source="&Server.MapPath(ConfigurationSettings.AppSettings("data")))

[loulanlouzhu]

da = New OleDbDataAdapter（delstring，conn）

[sharplee82]

还有很多其它命令的,如果用da = New OleDbDataAdapter（delstring，conn）
那下面的怎么办?
'插入命令
da.InsertCommand.CommandText = insertstring
da.InsertCommand.Connection = conn
'选择命令
da.SelectCommand.CommandText = selectstring
da.SelectCommand.Connection = conn
'更新命令
da.UpdateCommand.CommandText = updatestring
da.UpdateCommand.Connection = conn

[qiuji]

你是在DataGrid中使用的吗？
你可以这样来实现删除：（C#）
private void DataGrid1_DeleteCommand(object source, System.Web.UI.WebControls.DataGridCommandEventArgs e)
{
cn=new SqlConnection(ConfigurationSettings.AppSettings["ds"]);
string strSQL="delete from admin where adminid="+DataGrid1.DataKeys[(int)e.Item.ItemIndex];
cm=new SqlCommand(strSQL,cn);
cn.Open();
cm.ExecuteNonQuery();
cn.Close();
getData();//这里是你重新绑定数据到DataGrid的代码
}

[孟子E章]

http://xml.sz.luohuedu.net/xml/Content.asp

[saucer]

da.DeleteCommand = new OleDbCommand ( delstring, conn)

[sharplee82]

private sub form_load()
conn.Open()
conn = New OleDbConnection(Application("conn"))
da.DeleteCommand = New OleDbCommand(delstring, conn)'异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实
da.InsertCommand = New OleDbCommand(insertstring, conn)
da.SelectCommand = New OleDbCommand(selectstring, conn)
da.UpdateCommand = New OleDbCommand(updatestring, conn)
conn.Close()
end sub
以上的删除，插入更新选择都有在之前赋值。为什么会有da.DeleteCommand = New OleDbCommand(delstring, conn)'异常详细信息: System.NullReferenceException: 未将对象引用设置到对象的实

[saucer]

conn = New OleDbConnection(Application("conn"))
conn.Open()
da = New OleDbDataAdapter

da.DeleteCommand = New OleDbCommand(delstring, conn)
da.InsertCommand = New OleDbCommand(insertstring, conn)
da.SelectCommand = New OleDbCommand(selectstring, conn)
da.UpdateCommand = New OleDbCommand(updatestring, conn)

conn.Close()

[sharplee82]

不好意思,上面的conn.open在我程序中当然是放在下面一行.

conn = New OleDbConnection(Application("conn"))
conn.Open()刚才一时为了避免放很多代码在上面搞错.
5555555555555555555好急啊.有人知道怎么回事吗?

[sharplee82]

谢谢思归.