DataGridView中的复制（vb.net和ms-access数据库）

Question

每次执行它时，它都会使用新值复制数据并将其附加到DatagridView的先前内容中。我想清除内容然后添加新值..有人可以帮助我吗？ 这是我的代码：

Private Sub lvTable_ItemChecked(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ItemCheckedEventArgs) Handles lvTable.ItemChecked
    Try

        If lvTable.CheckedItems.Count > 0 Then
            Dim Condition As String = ""
            Dim Condition1 As String = ""
            For I = 0 To lvTable.CheckedItems.Count - 1

                Condition += String.Format("'{0}',", lvTable.CheckedItems(I).Text)
                Condition1 += String.Format("'{0}',", lvTable.CheckedItems(I).SubItems(1).Text)
            Next
            Condition = Condition.Substring(0, Condition.Length - 1)
            Condition1 = Condition1.Substring(0, Condition1.Length - 1)
            DataGridView2.Visible = True
            con = New OleDbConnection(cs)
            con.Open()
            Dim OleDb As String = "Select Item_ID,DishName, SUM(Qty), KOTGenerationItems.Rate, SUM(Amount), DiscPer, SUM(Disc), VATPer, SUM(VATAmt), STPer, SUM(STAmt), SCPer, SUM(SCAmt), SUM(TotalAmt),TableNo,GroupName from KOTGeneration,KOTGenerationItems,Dish where KOTGeneration.TicketID=KOTGenerationItems.Ticket_ID and KOTGenerationItems.Item_ID=Dish.ItemID and TableNo in (" & Condition & ") and GroupName in (" & Condition1 & ")   group by Item_ID,DishName,KOTGenerationItems.Rate,DiscPer,VATPer,STPer,SCPer,TableNo,GroupName order by TableNo"
            cmd = New OleDbCommand(OleDb, con)
            rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
            DataGridView2.Rows.Clear()
            While (rdr.Read() = True)
                DataGridView2.Rows.Add(rdr(0), rdr(1), rdr(2), rdr(3), rdr(4), rdr(5), rdr(6), rdr(7), rdr(8), rdr(9), rdr(10), rdr(11), rdr(12), rdr(13), rdr(14), rdr(15))
            End While
            con.Close()
            txtCash.Text = "0.00"
            TotalCalc1()
            Calc()
        Else
            Clear()
            DataGridView2.Rows.Clear()
            DataGridView2.Visible = False
        End If
    Catch ex As Exception
        MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
    End Try
End Sub