我的在线订单有问题，我已将所有下拉列表和按钮放在更新面板中，但是当我在下拉列表中选择某些内容或按下按钮时，整个页面发回...请帮助我！这是我的代码：` <%----%>
<strong><asp:ImageButton
ID="btnExcel0" runat="server" AlternateText="Export to Excel" Height="30px"
ImageUrl="/images/excel_icon1.png" onclick="btnExcel_Click" TabIndex="14" />
</strong>
<input type="image" runat ="server" id ="Image1" src ="/images/images.jpg" onclick="javascript:CallPrint('divPivot1')" title="Print" />
<br />
<div id= "divPivot1">
<asp:GridView ID="OrderGridView" runat="server" AllowPaging="True"
BorderStyle="None" CellPadding="3" DataKeyNames="Article"
EmptyDataText=""No product added..."" Font-Size="Small" HorizontalAlign="Left"
OnPageIndexChanging="OrderGridView_PageIndexChanging" PageSize="20"
TabIndex="15" Width="866px" BackColor="White" BorderColor="#CCCCCC"
BorderWidth="1px">
<FooterStyle BackColor="White" ForeColor="#336699" />
<HeaderStyle BackColor="#336699" Font-Bold="True" ForeColor="White" />
<PagerSettings FirstPageText="First" LastPageText="Last" />
<PagerStyle BackColor="White" ForeColor="#336699" HorizontalAlign="Left" />
<RowStyle ForeColor="#336699" Font-Size="Small" />
<SelectedRowStyle BackColor="#669999" Font-Bold="True" ForeColor="White" />
<SortedAscendingCellStyle BackColor="#F1F1F1" />
<SortedAscendingHeaderStyle BackColor="#007DBB" />
<SortedDescendingCellStyle BackColor="#CAC9C9" />
<SortedDescendingHeaderStyle BackColor="#00547E" />
<Columns>
<asp:TemplateField HeaderText="Delete" ItemStyle-HorizontalAlign="Center" >
<ItemTemplate>
<asp:CheckBox ID="CheckBox1" runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Update Quantity" ItemStyle-HorizontalAlign="Center" ItemStyle-Width="80">
<ItemTemplate>
<asp:TextBox ID="TextBox" runat="server" Width="90" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
br />
<br />
<asp:Label ID="lblsum" runat="server" CssClass="style19" Text="Sum Total"></asp:Label>
<br />
<asp:Label ID="sum" runat="server" CssClass="style19"></asp:Label>
<br />
</div>
<strong><asp:ImageButton ID="btnDelete" runat="server" Height="28px"
ImageUrl="/images/bt_Delete.jpg" onclick="btnDelete_Click"
OnClientClick="return DeleteConfirmation();" TabIndex="13" Width="106px" />
</strong> <asp:ImageButton ID="btnUpdate"
runat="server" Height="28px" ImageUrl="/images/btUpdate.jpg" Width="106px"
OnClientClick="return UpdateConfirmation();"
onclick="btnUpdate_Click" />
<asp:TextBox ID="username" runat="server" Height="16px" Visible="False"
Width="128px"></asp:TextBox>
<br />
<asp:Label ID="Label16" runat="server" Text="Notes:" ForeColor="#336699"></asp:Label>
<br />
<asp:TextBox ID="TextBox5" runat="server" Height="101px" TabIndex="10"
TextMode="MultiLine" Width="860px"></asp:TextBox>
<br />
<asp:ImageButton
ID="btnSend" runat="server" ImageUrl="/images/mail2.jpg"
onclick="Button1_Click" AlternateText="Send your Order"
TabIndex="11" Height="75px" Width="90px"/><strong><asp:ImageButton
ID="ImageButton1" runat="server" Height="66px"
ImageUrl="/images/logout.png" Width="56px"
onclick="ImageButton1_Click" />
</strong>
<br />
<strong>
<asp:Label ID="Label18" runat="server" style="color: #336699"
Text="*Delete Product from List: Check the products which you want to remove from your list and press the delete button."></asp:Label>
</strong>
</ContentTemplate>
<Triggers>
<asp:PostBackTrigger ControlID="btnExcel0" />
<asp:AsyncPostBackTrigger ControlID="ImageButton1" />
<asp:AsyncPostBackTrigger ControlID="code" EventName="SelectedIndexChanged" />
<asp:AsyncPostBackTrigger ControlID="type" EventName="SelectedIndexChanged" />
<asp:AsyncPostBackTrigger ControlID="p" EventName="SelectedIndexChanged" />
<asp:AsyncPostBackTrigger ControlID="dem" EventName="SelectedIndexChanged" />
<asp:AsyncPostBackTrigger ControlID="quant" EventName="TextChanged" />
<asp:AsyncPostBackTrigger ControlID="btnAdd" />
<asp:AsyncPostBackTrigger ControlID="btnDelete" />
<asp:AsyncPostBackTrigger ControlID="btnUpdate" />
<asp:AsyncPostBackTrigger ControlID="btnSend" />
</Triggers>
</asp:UpdatePanel>`