I am creating a POS system with access database, anyway this is my code

Imports System.Data.OleDb
Public Class MainSeller
    Dim cnn As New OleDb.OleDbConnection
    Dim cmdDelete As New OleDb.OleDbCommand
    Dim cnnOLEDB As New OleDb.OleDbConnection
    Dim cmdInsert As New OleDb.OleDbCommand
    Dim cmdUpdate As New OleDb.OleDbCommand
    Dim strConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" &
     System.Environment.CurrentDirectory & "\InventSystem.accdb"
    Public Sub RefreshData()
        If Not cnn.State = ConnectionState.Open Then
            'open connection
            cnn.Open()
        End If

        Dim da As New OleDb.OleDbDataAdapter("SELECT Barcode, " & _
                                          "ItemName as [Item Name], ItemDescription, Quantity, TotalPrice " & _
                                          " FROM ReceiptDetails ORDER BY ReceiptID", cnn)
        Dim dt As New DataTable
        'fill data to datatable
        da.Fill(dt)

        'offer data in data table into datagridview
        Me.DataGridView1.DataSource = dt

        'close connection
        cnn.Close()
        'DataGridView1.DataSource = ds.Tables(0)
    End Sub