Question

我是VB 2010的新手。我一直在尝试使用ms访问作为数据库开发一个小型数据库。我不知道为什么我得到这个错误＆＃34;对象引用未设置为对象的实例。＆＃34;。我已经尝试了很多网站，但在网站上没有适当的解决方案。我的代码是：

Public Class Form1
Dim con As New OleDbConnection()
Dim ds As New DataSet
Dim inc As Integer
Dim maxRows As Integer
Dim sql_query As String
Dim da As OleDbDataAdapter
Dim cmd As New OleDbCommand

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    con.ConnectionString = "PROVIDER=MICROSOFT.JET.OLEDB.4.0;DATA SOURCE=C:\BILL\BILL_DATA.MDB"
    con.Open()
    MsgBox("Opened")

    sql_query = "SELECT * FROM tblBill"
    da = New OleDb.OleDbDataAdapter(sql_query, con)
    da.Fill(ds, "tblBill")
    con.Close()

End Sub

Private Sub btnQuit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnQuit.Click
    End
End Sub

Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
    If inc <> -1 Then

        Dim cb As OleDbCommandBuilder = New OleDbCommandBuilder(da)
        Dim ds As DataSet = New DataSet

        Dim dt As DataTable = ds.Tables("tblBill")

        Dim newRow As DataRow = dt.NewRow()


        newRow.Item("BillNo") = txtBillNo.Text
        newRow.Item("BillDate") = dtpApprDate.Text
        newRow.Item("Party") = txtParty.Text

        dt.Rows.Add(newRow)
        da.Update(ds, "tblBill")
    End If
End Sub
End Class

VB 2010错误：对象引用未设置为对象的实例

0 个答案: