我改成这样:

Private Sub btnDelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDelete.Click
If (Me.BindingContext(objDataSet1, "ad_class").Count > 0) Then
Me.BindingContext(objDataSet1, "ad_class").RemoveAt(Me.BindingContext(objDataSet1, "ad_class").Position)
Me.objDataSet1_PositionChanged()
str = "select * from ad_class"
Dim da As New OleDbDataAdapter(Str, cnnstr)
Dim db As New OleDbCommandBuilder(da)
da.Update(objDataSet1, "ad_class")

End If
End Sub
出现以下错误:

未处理的“System.InvalidOperationException”类型的异常出现在 system.data.dll 中。

其他信息: DataAdapter.SelectCommand.Connection 属性需要初始化；
怎么办呀???????????????????????

我在代码外面有定义:
Public cnnstr As OleDbConnection
Public str As String

谁能帮我呀?
给我完整一点的代码呀..我是新手急着用呀..谢谢..

我自己试了很多次了/...实在不行呀...

dim da as oledbadapter
dim ds as new dataset
dim str as string="select * from tablename"
dim cnnstr as sting=" " ’自己写
Private Sub form_load()
da=new oledbadapter(str,cnnstr)
da.fill(ds,tablename)
绑定数据
end sub

Private Sub btnDelete_Click()
If (Me.BindingContext(ds, "tablename").Count > 0) Then
Me.BindingContext(ds, "tablename").RemoveAt(Me.BindingContext(ds, "tablename").Position)
Me.BindingContext(ds, "tablename").endcurrentedit
Dim db As New OleDbCommandBuilder(da)
da.Update(ds, "tablename")
End If
End Sub

我再去试试........

..................

不知道你还会不会在呢? 我也是一个新手,很愿意和你交流一下.
我到是实现了删除数据,以下是我的代码,你先参考一下:

Imports System.Data.OleDb
Public Class Form1
Const AssociatorInfoSql As String = "SELECT * FROM AssociatorInfo ORDER BY UserID"
Const ConsumeInfoSql As String = "SELECT * FROM ConsumeInfo ORDER BY UserID"
Dim ConnString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Environment.CurrentDirectory & "\Associator.mdb"
Dim XTQConn As New OleDbConnection(ConnString)
Dim XTQAdapter As OleDbDataAdapter
Dim XTQDataSet As New DataSet

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
XTQConn.Open()
'填充Associatorinfo表
XTQAdapter = New OleDbDataAdapter(AssociatorInfoSql, XTQConn)
XTQDataSet.Tables.Add("AssInfoTable") '添加一个表ASSINFOTABLE在xtqdataset中
XTQAdapter.Fill(XTQDataSet, "AssInfoTable")
XTQAdapter.Dispose()

XTQAdapter = New OleDbDataAdapter(ConsumeInfoSql, XTQConn)
XTQDataSet.Tables.Add("ConsumeInfoTable")
XTQAdapter.Fill(XTQDataSet, "ConsumeInfoTable")
XTQAdapter.Dispose()

XTQConn.Close()

DGViewAss.DataSource = XTQDataSet.Tables("AssInfoTable")
dgViewConsume.DataSource = XTQDataSet.Tables("ConsumeInfoTable")
End Sub

Private Sub btnDelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDelete.Click
DGViewAss.Rows.Remove(DGViewAss.CurrentRow)
SaveChanges()
End Sub

Private Sub SaveChanges()
Try
If XTQDataSet.HasChanges Then
XTQDataSet.AcceptChanges()
XTQConn.Open()
XTQAdapter = New OleDbDataAdapter(AssociatorInfoSql, XTQConn)
Dim Builder As New OleDbCommandBuilder(XTQAdapter)
XTQAdapter.Update(XTQDataSet.Tables("AssInfotable"))
MessageBox.Show("保存成功")
Builder.Dispose()
XTQConn.Close()
btnSaveChange.Enabled = False
End If
Catch ex As Exception
MessageBox.Show("保存数据时错误，请检查程序状态！", "保存数据", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
Finally
XTQConn.Close()
End Try
End Sub
End Class

我想,你的代码改成这样试试,看行不行:

Private Sub btnDelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDelete.Click
If (Me.BindingContext(objDataSet1, "ad_class").Count > 0) Then
Me.BindingContext(objDataSet1, "ad_class").RemoveAt(Me.BindingContext(objDataSet1, "ad_class").Position)
Me.objDataSet1_PositionChanged()
objDataSet1.AcceptChanges() '这是我加的
Dim da As New OleDbDataAdapter(Str, cnnstr)
Dim db As New OleDbCommandBuilder(da)
da.Update(objDataSet1, "ad_class")

End If
End Sub

OleDbDataAdqpter对象的两个参数中,第一个参数是SQL命令字符串,第二个参数是OleDbConnection对象.
我在我的机子上,没有我加的那句,也是会出错的.

对了,我用的是VS2005

谢谢你们...我的可以了....
如果可以的话..加我QQ287045741 大家一起研究!!

问题解决了...谢谢!!!!!!!!!!!

我知道在Sqlser数据库中也存在这样的现象，解决方法如下
Dim mycon As Sqlconnection("连接字符传,包括用户名，密码，数据库名，服务器名")
Dim sqlstr As String
Dim myadapter As SqlDataAdapter("sqlstr-也就是sql命令",mycon)
Dim myset As DataSet
myadapter.Fill(myset,"表名")
Dim rowno As Integer
rowno=DataGrid1.CurrentRowIndex
myset.表名.Rows(rowno).Delete()
此时只是在内存中的数据库表myset中的内容删除了，而在实际数据库中的内容却没有删除
还应该加上
myadapter.Update(myset.Getchanges)