System.Data.dll中发生了'System.Data.OleDb.OleDbException'类型的第一次机会异常

Question

这是我的代码问题是，每次运行它时都会说数据已经存在，并在下面的即时窗口中显示一条消息（System.Data中发生类型System.Data.OleDb.OleDbException的第一次机会异常）。 dll）目前我们在学校使用vb 10 express并且在访问中使用12.0并不是很好用

Imports System.Data
Imports System.Data.OleDb

Public Class Form1

Dim con As New OleDbConnection
Dim Com As New OleDbCommand
Dim ComInsert As New OleDbCommand
Dim ComUpdate As New OleDbCommand
Dim ComDelete As New OleDbCommand
Dim aAdapter As New OleDbDataAdapter
Dim Dset As New DataSet

'Dim dRead As New OleDbDataReader

Private Sub FrmCustomer_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Dim ConProvider As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=H:\richardnew.mdb"

    Try
        con.ConnectionString = ConProvider
        If Not con.State = ConnectionState.Open Then
            con.Open()

            MsgBox("Connection Established")
        End If
    Catch ex As Exception
        MsgBox("No Connection Established")
    End Try

    ListView1.Columns.Add("Customer No", 100, HorizontalAlignment.Left)
    ListView1.Columns.Add("Name", 300, HorizontalAlignment.Left)
    ListView1.Columns.Add("City", 300, HorizontalAlignment.Left)
    ListView1.View = View.Details
    ListView1.GridLines = True
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Try
        Try
            If Not con.State = ConnectionState.Open Then
                con.Open()
            End If
        Catch ex As Exception
            MsgBox(ex.Message, MsgBoxStyle.Information, "ERROR CONNECTION")

        End Try

        If TextBox3.Text = "" Or TextBox2.Text = "" Then
            MsgBox("All Fields are required, Check the fields", MsgBoxStyle.Information, "Required Fiels")
            Exit Sub
        End If

        With aAdapter
            .SelectCommand = New OleDb.OleDbCommand()
            .SelectCommand.CommandText = "select * from [customer] where cust-no = '" & TextBox1.Text & "'"
            .SelectCommand.Connection = con
        End With

        Dim dataRead As OleDb.OleDbDataReader
        dataRead = aAdapter.SelectCommand.ExecuteReader()

        If Not dataRead.HasRows Then
            ComInsert.CommandText = "INSERT INTO customer(cust-no,cust-name,cust-city)" & _
                "VALUES('" & TextBox1.Text & "','" & TextBox2.Text & "','" & TextBox3.Text & "')"

            ComInsert.Connection = con
            ComInsert.ExecuteNonQuery()

            MsgBox(TextBox1.Text & " has been added to the record", MsgBoxStyle.Information, "NEW RECORD")

            TextBox1.Text = ""
            TextBox2.Text = ""
            TextBox3.Text = ""

            aAdapter.Dispose()
            ComInsert.Dispose()

        Else
            MsgBox("WARNING1: Customer Already Exist in the Record!!", MsgBoxStyle.Exclamation, "ERROR SAVING DATA")
        End If
    Catch ex As Exception

        MsgBox("WARNING2: Customer Number Already Exist in the Record!!", MsgBoxStyle.Exclamation, "ERROR SAVING DATA")
        TextBox1.Focus()
        Exit Sub

    End Try
    Call lvpop()
End Sub
Public Sub lvpop()
    ListView1.Clear()
    ListView1.Items.Clear()
    With ListView1
        .Columns.Add("Customer No", 100, HorizontalAlignment.Left)
        .Columns.Add("Name", 300, HorizontalAlignment.Left)
        .Columns.Add("City", 300, HorizontalAlignment.Left)
        .View = View.Details
        .GridLines = True
    End With
    With aAdapter
        .SelectCommand = New OleDb.OleDbCommand()
        .SelectCommand.CommandText = "select * from [customer] where cust-no = '" & TextBox1.Text & "'"
        .SelectCommand.Connection = con
    End With

    Dim dataRead As OleDb.OleDbDataReader
    dataRead = aAdapter.SelectCommand.ExecuteReader()

    Do While dataRead.Read()
        Dim Item As New ListViewItem

        Item.Text = IIf(dataRead.IsDBNull(0), "", dataRead.Item(0))

        For sItems = 1 To dataRead.FieldCount() - 1
            If Not dataRead.IsDBNull(sItems) Then
                Item.SubItems.Add(dataRead.Item(sItems))
            Else
                Item.SubItems.Add("")
            End If
        Next sItems
        Me.ListView1.Items.Add(Item)
    Loop
End Sub
End Class