Access 数据库不会显示在 VB.NET DGV with Button 中。连接打不开

Access database won't show in VB.NET DGV with Button. Connection won't open

Imports System.Data.OleDb
 Public Class Form1

    Dim dbConnection As OleDbCommand
    Dim dbCommand As OleDbCommand
    Dim dbDataAdapter As OleDbDataAdapter
    Dim ConnectString As String = "Provider = Microsoft.ACE.OLEDB.12. , Data    Source = PatientBilling.mdb.accdb "
    Dim dtPatientBillingTable As DataTable
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As  System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub dispAll_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles dispAll.Click
        dbConnection = New OleDbConnection() 
        dbDataAdapter = New OleDbDataAdapter()
        dtPatientBillingTable = New DataTable()
        dbCommand = New OleDbCommand("SELECT * FROM PatientBillingTable")
        dbCommand.CommandType = CommandType.TableDirect
        dbDataAdapter.SelectCommand = dbCommand
        dbDataAdapter.SelectCommand.Connection = dbConnection
        dbConnection.Open() 
        dbDataAdapter.Fill(dtPatientBillingTable)
        DataGridView1.DataSource = dtPatientBillingTable
        dbConnection.Close() 

    End Sub
End Class

-连接打不开 - 按钮不起作用

尝试改变这个:

dbConnection = New OleDbConnection() 

对此:

dbConnection = New OleDbConnection(ConnectString)