รบกวนช่วยหน่อยค่ะ Debug แล้วเจอ Error : input string was not in a correct format

            Using ts As New TransactionScope()
                Dim FirstID As String = ""
                Dim SecondID As Integer = 0
                Dim csids = From cid In db.CashSales _
                            Order By cid.SaleID Descending Take (1)

                Dim LastSaleID As String = ""
                If csids.Count() = 1 Then
                    FirstID = csids.SingleOrDefault().SaleID.Left(4)
                    SecondID = Integer.Parse(csids.SingleOrDefault().SaleID.Right(6))   'Error บรรทัดนี้ค่ะ                    SecondID += 1
                    LastSaleID = String.Format(FirstID, "0000") & SecondID.ToString("000000")
                Else
                    LastSaleID = BizConfig.CurrentBranchID & "000001"
                End If