DropDownList二级联动 为何子级DropDownList 显示不出来啊 求助！

Question

你有把DropDownList2的AutoPostBack設為true嗎

Answer 1

要想实现联动必须把DropDownList的AutoPostBack属性设置true，这样才能回传服务器，获得数据

Answer 2

代码没错，应该是1楼的问题，或者SQL查询根本查不到数据
不过建议DataSet用完要dispose()掉，占缓存资源

Answer 3

参考:http://download.csdn.net/source/331627http://download.csdn.net/source/282546

Answer 4

DataBind() 
你这个函数时放在pageload里面的么，如果是，那么有没有写if(!this.page.ispostback){DataBind(); }

Answer 5

选择第一个DropDownList是否页面有刷新的迹象？

Answer 6

<td style="text-align: right;">分类1：</td>
                                    <td style="width :220px;text-align: left">
                                        <asp:DropDownList ID="ddlclass1" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource1"
                                            DataTextField="RSS_CLASS_NAME" DataValueField="RSS_CLASS_ID" Width="101px" OnSelectedIndexChanged="ddlclass1_SelectedIndexChanged" >
                                        </asp:DropDownList>
                                        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:RSSConnectionString %>"
                                            SelectCommand="SELECT RSS_CLASS_ID, RSS_CLASS_NAME, RSS_CLASS_SERIES, RSS_FATHER_ID FROM RSS_CLASS WHERE (RSS_FATHER_ID = @fatherID) AND (RSS_CLASS_SERIES = @seriesID) OR (RSS_CLASS_ID = @classID2) ORDER BY RSS_CLASS_ID"
                                            ProviderName="<%$ ConnectionStrings:RSSConnectionString.ProviderName %>">
                                            <SelectParameters>
                                                <asp:Parameter DefaultValue="000" Name="fatherID" />
                                                <asp:Parameter DefaultValue="1" Name="seriesID" />
                                                <asp:Parameter DefaultValue="000" Name="classID2" />
                                            </SelectParameters>
                                        </asp:SqlDataSource>                               
                                    </td>                                   
                                    <td style="text-align: right">分类2：</td>
                                    <td style="width :220px;text-align: left">
                                       <asp:DropDownList ID="ddlclass2" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource2"
                                            DataTextField="RSS_CLASS_NAME" DataValueField="RSS_CLASS_ID" Width="101px" >
                                        </asp:DropDownList>
                                        <asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:RSSConnectionString %>"
                                            SelectCommand="SELECT RSS_CLASS_ID, RSS_CLASS_NAME, RSS_FATHER_ID, RSS_CLASS_SERIES FROM RSS_CLASS WHERE (RSS_FATHER_ID = @fatherID) AND (RSS_CLASS_SERIES = @series) OR (RSS_CLASS_ID = @classId2) ORDER BY RSS_CLASS_ID"
                                            ProviderName="<%$ ConnectionStrings:RSSConnectionString.ProviderName %>">
                                            <SelectParameters>
                                                <asp:ControlParameter ControlID="ddlclass1" Name="fatherID" PropertyName="SelectedValue" />
                                                <asp:Parameter DefaultValue="2" Name="series" />
                                                <asp:Parameter DefaultValue="000" Name="classId2" />
                                            </SelectParameters>
                                        </asp:SqlDataSource>
                                    </td>                                   
                                    <td style="text-align: right">分类3：</td>
                                    <td style="width :210px;text-align: left">
                                          <asp:DropDownList ID="ddlclass3" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource3"
                                            DataTextField="RSS_CLASS_NAME" DataValueField="RSS_CLASS_ID" Width="101px">
                                        </asp:DropDownList>                                     
                                        <asp:SqlDataSource ID="SqlDataSource3" runat="server" ConnectionString="<%$ ConnectionStrings:RSSConnectionString %>"
                                            ProviderName="<%$ ConnectionStrings:RSSConnectionString.ProviderName %>" SelectCommand="SELECT RSS_CLASS_ID, RSS_CLASS_NAME, RSS_FATHER_ID, RSS_CLASS_SERIES FROM RSS_CLASS WHERE (RSS_FATHER_ID = @fatherID AND RSS_CLASS_SERIES = @seriesID)&#13;&#10;OR (RSS_CLASS_ID = @classId2) ORDER BY RSS_CLASS_ID">
                                            <SelectParameters>
                                                <asp:ControlParameter ControlID="ddlclass2" Name="fatherID" PropertyName="SelectedValue" />
                                                <asp:Parameter DefaultValue="3" Name="seriesID" />
                                                <asp:Parameter DefaultValue="000" Name="classId2" />
                                            </SelectParameters>
                                        </asp:SqlDataSource>
  
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Answer 7

你的 DropDownList2 selectindexchanged事件触发时，是否可以进入此事件对应的你写的函数