为什么当我在 datagridview1 中按搜索两次时出现接收错误？

问：

我有这个代码，我认为似乎工作正常，当我编写代码并按回车键在txt_searchProduct_barcode处搜索时，插入 datagridview1 并在列中显示所有产品信息到目前为止一切正常，但是当我再次搜索以计算quatity和总数时......在最后一列中，它总是给出价格列中零的结果，以及 datagridview1 的最后一列，这里是子代码......

    Dim exist As Boolean = False, numrow As Integer = 0, numtext As Integer
    For Each itm As DataGridViewRow In DataGridView1.Rows
        If itm.Cells(0).Value IsNot Nothing Then
            If itm.Cells(1).Value.ToString = txt_searchProduct_barcode.Text Then
                exist = True
                numrow = itm.Index
                numtext = CInt(itm.Cells(8).Value)
                Exit For
            End If
        End If
    Next
    If exist = False Then
        Try
            conn.Open()
            cmd = New MySqlCommand("SELECT * FROM `tblproduct` WHERE `procode`='" & txt_searchProduct_barcode.Text & "'", conn)
            dr = cmd.ExecuteReader
            While dr.Read()
                If txt_searchProduct_barcode.Text = String.Empty Then
                    Return
                Else
                    'Create new row.
                    ' `procode`, `proname` , `progroup` , `uom` , `location` , `price` , `tax` , `totalprice`
                    Dim procode As String = dr("procode")
                    Dim Proname As String = dr("proname")
                    Dim Progroup As String = dr("progroup")
                    Dim uom As String = dr("uom")
                    Dim Price As Decimal = dr("price")
                    Dim tax As Decimal = dr("tax")
                    Dim totalprice As Decimal = dr("totalprice")

                    Dim totalqtyprice As Double

                    totalqtyprice = Price * tax / 100 + Price

                    DataGridView1.Rows.Add(DataGridView1.Rows.Count + 1, procode, Proname, Progroup, uom, Price, tax, totalprice, 1, totalqtyprice)


                End If
            End While
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            conn.Close()
        End Try
    Else
        DataGridView1.Rows(numrow).Cells(8).Value = CInt("1") + numtext
        DataGridView1.Rows(numrow).Cells(9).Value = DataGridView1.Rows(numrow).Cells(7).Value * DataGridView1.Rows(numrow).Cells(8).Value
    End If
End Sub

我想了解错误在哪里以及如何更改。谢谢