关于dropdownlist的SelectedIndexChanged事件无法触发！

Question

我用了4个dropdownlist，4级联动，动态绑定上去的。
当选择后要把跟这4个dropdownlist相关的内容查询并显示出来，但是SelectedIndexChanged事件
无法触发，我在网上也搜索了很多这方面的问题都无法解决，但是我自己只用1个dropdownlist试了
下，发现只用一个dropdownlist时可以触发事件，但是用4级联动后就无法触发事件了。
请大家帮帮忙，看下是什么情况造成的，我的事件是在dropdownlist的属性，然后选择
SelectedIndexChanged双击的，并且也设置了AutoPostBack="True" ，事件里也加
了if（！page.ispostback）。

Answer 1

 <asp:DropDownList ID="DropDownList1" Width="120px" runat="server" AutoPostBack="True">
                                                                                                    <asp:ListItem Selected="True">请选择产地</asp:ListItem>
                                                                                                    <asp:ListItem>国产汽车</asp:ListItem>
                                                                                                    <asp:ListItem>进口汽车</asp:ListItem>
                                                                                                </asp:DropDownList>
                                                                                                <asp:DropDownList ID="DropDownList2" Width="120px" runat="server" AutoPostBack="True"
                                                                                                    DataSourceID="SqlDataSource1" DataTextField="chinese" DataValueField="chinese">
                                                                                                </asp:DropDownList><asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:521che_comConnectionString %>"
                                                                                                    SelectCommand="SELECT [chinese], [chandi] FROM [t_cars_brand] WHERE ([chandi] = @chandi)">
                                                                                                    <SelectParameters>
                                                                                                        <asp:ControlParameter ControlID="DropDownList1" DefaultValue="null" Name="chandi"
                                                                                                            PropertyName="SelectedValue" Type="String" />
                                                                                                    </SelectParameters>
                                                                                                </asp:SqlDataSource>
                                                                                                <asp:DropDownList ID="DropDownList3" Width="120px" runat="server" AutoPostBack="True"
                                                                                                    DataSourceID="SqlDataSource2" DataTextField="cartype" DataValueField="cartype">
                                                                                                </asp:DropDownList><asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:521che_comConnectionString %>"
                                                                                                    SelectCommand="SELECT [pinpai], [chandi], [cartype] FROM [t_cars_type] WHERE (([pinpai] = @pinpai) AND ([chandi] = @chandi))">
                                                                                                    <SelectParameters>
                                                                                                        <asp:ControlParameter ControlID="DropDownList2" Name="pinpai" PropertyName="SelectedValue"
                                                                                                            Type="String" />
                                                                                                        <asp:ControlParameter ControlID="DropDownList1" Name="chandi" PropertyName="SelectedValue"
                                                                                                            Type="String" />
                                                                                                    </SelectParameters>
                                                                                                </asp:SqlDataSource>
                                                                                                <asp:DropDownList ID="DropDownList4" Width="120px" runat="server" DataSourceID="SqlDataSource3"
                                                                                                    DataTextField="subtype" DataValueField="subtype" AutoPostBack="True" OnSelectedIndexChanged="DropDownList4_SelectedIndexChanged">
                                                                                                </asp:DropDownList><asp:SqlDataSource ID="SqlDataSource3" runat="server" ConnectionString="<%$ ConnectionStrings:521che_comConnectionString %>"
                                                                                                    SelectCommand="SELECT [subtype], [xilie] FROM [t_cars_subtype] WHERE (([xilie] = @xilie) AND ([chandi] = @chandi) AND ([pinpai] = @pinpai))">
                                                                                                    <SelectParameters>
                                                                                                        <asp:ControlParameter ControlID="DropDownList3" Name="xilie" PropertyName="SelectedValue"
                                                                                                            Type="String" />
                                                                                                        <asp:ControlParameter ControlID="DropDownList1" Name="chandi" PropertyName="SelectedValue"
                                                                                                            Type="String" />
                                                                                                        <asp:ControlParameter ControlID="DropDownList2" Name="pinpai" PropertyName="SelectedValue"
                                                                                                            Type="String" />
                                                                                                    </SelectParameters>
                                                                                                </asp:SqlDataSource>
  protected void DropDownList4_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                if (this.DropDownList1.SelectedValue == "请选择产地")
                {
                    pic = "car/images/selectModel_blank.gif";                }
                else
                {
                    string sql = "select * from t_newcar where pinpai='" + this.DropDownList2.SelectedValue + "' and xilie='" + this.DropDownList3.SelectedValue + "' and chexing='" + this.DropDownList4.SelectedValue + "'";
                    DataSet ds = Maticsoft.DBUtility.DbHelperSQL.Query(sql);
                    DataTable dt = ds.Tables[0];
                  
                    pinpai = dt.Rows[0]["pinpai"].ToString();
                    chexing = dt.Rows[0]["chexing"].ToString();
                    leixing = dt.Rows[0]["newcar_type"].ToString();
                    changshang = dt.Rows[0]["newcar_factory"].ToString();
                    year = dt.Rows[0]["newcar_year"].ToString();
                    pic = "img/cars_image/";
                    pic += dt.Rows[0]["newcar_image"].ToString();
                    price = dt.Rows[0]["clear_price"].ToString();
                }
            }
        }

Answer 2

who  can  help me?

Answer 3

你把你的DataSourceID去掉！！！用事件绑定，控件.DataSource= "你查出的数据"。不行吗？？
有是数据源绑定，又是后台DataSource赋值，我看的有点晕！！

Answer 4

在你的ddl_change事件的第一句代码处设置断断点。
单步调试才是解决问题的王道。

Answer 5

在DropDownList的SelectedIndexChanged事件中还要绑定一次:
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownList2.DataBind();
        DropDownList3.DataBind();
        DropDownList4.DataBind();
    }    protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownList3.DataBind();
        DropDownList4.DataBind();
    }    protected void DropDownList3_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownList4.DataBind();
    }不太明白你在DropDownList4_SelectedIndexChanged的代码
既然用SqlDataSource为什么还用传统的.

Answer 6

我也出现过这种情况，我当时是把dropdownlist的autopostback属性选上后就可以触发该事件了~~~