DropdownList异步刷新GridView数据

前台代码：

    <div style=" clear:both; width:800px; text-align:center; margin-left:auto; margin-right:auto; margin-left:270px">

    <table>

        <tr>

            <td style="font-weight: bold; font-size: 20px; text-align: center"

                class="style556">

                <asp:Label ID="lblTitle" runat="server"></asp:Label>

            </td>

        </tr>

        <tr>

            <td align="right">

              时间：<asp:DropDownList ID="ddlDate" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlDate_SelectedIndexChanged">

                    </asp:DropDownList>

                     

            </td>

        </tr>

        <tr>

            <td style="text-align:right">

                <asp:UpdatePanel ID="UpdatePanel1" runat="server">

                    <ContentTemplate>

                <yyc:SmartGridView ID="sgvFile" runat="server" AllowPaging="True" AutoGenerateColumns="False"

                    DataKeyNames="Id" OnPageIndexChanging="SmartGridView_PageIndexChanging" PageSize="30"

                    SkinID="UnpagedWrap" Width="790px" MergeCells="5,6,7,8">

                    <Columns>

                        <asp:BoundField DataField="Id" HeaderText="Id" Visible="False" />

                        <asp:TemplateField HeaderText="方向">

                            <ItemTemplate>

                                <asp:Label ID="lbyinyong" runat="server" Text='<%# Eval("LeftOrRight").ToString()=="1"?"进洞口":"出洞口" %>'></asp:Label>

                            </ItemTemplate>

                            <ItemStyle Width="70px" />

                        </asp:TemplateField>

                        <asp:BoundField DataField="ClassName" HeaderText="工序名称" />

                        <asp:BoundField DataField="AllLength" DataFormatString="{0:0.##}" HeaderText="长度<br/>"

                            HtmlEncode="False" />

                        <asp:TemplateField HeaderText="截止上日末<br/>数量(m)">

                            <ItemTemplate>

                                <%# Convert.ToInt32(Eval("LeftOrRight")) == 1 ? Eval("AllFinishL") : Eval("AllFinishR")%>

                            </ItemTemplate>

                        </asp:TemplateField>

                        <asp:BoundField DataField="FinishNumber" DataFormatString="{0:0.##}" HeaderText="本日数量<br/>(m)"

                            HtmlEncode="False" />

                        <asp:BoundField DataField="AllFinish" DataFormatString="{0:0.##}" HeaderText="累计完成<br/>数量(m)"

                            HtmlEncode="False" />

                        <asp:BoundField DataField="PercentFinish" DataFormatString="{0:0.##}%" HeaderText="累计完成<br/>百分比"

                            HtmlEncode="False" />

                        <asp:BoundField DataField="NoFinishNumber" DataFormatString="{0:0.##}" HeaderText="剩余量<br/>(m)"

                            HtmlEncode="False" />

                        <asp:BoundField DataField="AddDate" DataFormatString="{0:d}" HeaderText="日期" HtmlEncode="False"

                            ReadOnly="True">

                            <ItemStyle HorizontalAlign="Center" />

                        </asp:BoundField>

                        <asp:TemplateField HeaderText="监理<br>审核">

                            <ItemTemplate>

                                <asp:Label ID="Label1" Text='<%# zhy_CommClass.zhyPageView.IsPassView(Eval("Pass"), "已审", "<font color=red>未审</font>")                                         %>' runat="server"></asp:Label>

                            </ItemTemplate>

                        </asp:TemplateField>

                    </Columns>

                </yyc:SmartGridView>

                 </ContentTemplate>

                 <Triggers>

                 　　<asp:AsyncPostBackTrigger ControlID="ddlDate" />

                 </Triggers>

                </asp:UpdatePanel>

            </td>

        </tr>

    </table>

    </div>