gridview 怎么自动计算文本框值
                              <asp:TemplateField ItemStyle-Width="40px" HeaderText="单价">
                        <ItemStyle HorizontalAlign="Center" />
                        <HeaderStyle HorizontalAlign="Center" />
                            <ItemTemplate>
                                <asp:TextBox ID="lblPrice" runat="server" Width="40px" Text='<%#Eval("Price") %>'    />
                            </ItemTemplate>
                        </asp:TemplateField>

                        <asp:TemplateField ItemStyle-Width="40px" HeaderText="数量">
                        <ItemStyle HorizontalAlign="Center" />
                        <HeaderStyle HorizontalAlign="Center" />
                            <ItemTemplate>
                                <asp:TextBox ID="txtNumber" runat="server" Width="40px" Text="1"     />
                            </ItemTemplate>
                        </asp:TemplateField>