Multiply in Datalist

<asp:datalist id="DataList1" datakeyfield="id" runat="server" xmlns:asp="#unknown">
                <itemtemplate>
                    Price:<asp:label id="Label5" runat="server" text="<%#Eval("PRICE") %>"></asp:label>
                    Quantity:<asp:dropdownlist id="DropDownList1" runat="server" onselectedindexchanged="DropDownList1_SelectedIndexChanged" autopostback="true">
                        <asp:listitem text="0" value="0" selected="True"></asp:listitem>
                        <asp:listitem text="1" value="1"></asp:listitem>
                        <asp:listitem text="2" value="2"></asp:listitem>
                        <asp:listitem text="3" value="3"></asp:listitem>
                        <asp:listitem text="4" value="4"></asp:listitem>
                        <asp:listitem text="5" value="5"></asp:listitem>
                    </asp:dropdownlist>
                    Total:<asp:label id="Label7" runat="server"></asp:label>
                </itemtemplate>
            </asp:datalist>



protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        var ddlList = (DropDownList)sender;
        var row = (DataListItem)ddlList.NamingContainer;
        int index = row.ItemIndex;
        var p = Convert.ToInt32(((Label)row.FindControl("Label5")).Text);
        var q = Convert.ToInt32(ddlList.SelectedItem.Value);
        var res = Convert.ToInt32(p * q);
        Label lblRes = ((Label)row.FindControl("Label7"));
        lblRes.Text = res.ToString();
    }