WebForm 三级联动

三级联动

数据库根据父级代号条件写查询 返回list<>集合

方法一：

创建三个下拉列表：

※AutoPostBack：否发生自动回传到服务器的操作。如果把该属性设置为 TRUE，则启用自动回传，否则为 FALSE。默认是 FALSE。

 省：<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"></asp:DropDownList>
 市：<asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True"></asp:DropDownList>
 区：<asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True"></asp:DropDownList>

CS：

※SelectedIndexChanged事件：当列表控件的选定项在信息发往服务器之间变化时发生

     protected void Page_Load(object sender, EventArgs e)
     {
         if (!IsPostBack)
         {
             Bind(new ChinaStatesDA().Select(""), DropDownList1);
             Bind(new ChinaStatesDA().Select(DropDownList1.SelectedValue), DropDownList2);
             Bind(new ChinaStatesDA().Select(DropDownList2.SelectedValue), DropDownList3);
         }
         DropDownList1.SelectedIndexChanged += DropDownList1_SelectedIndexChanged;
         DropDownList2.SelectedIndexChanged += DropDownList2_SelectedIndexChanged;
     }

     void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
     {
         Bind(new ChinaStatesDA().Select(DropDownList2.SelectedValue), DropDownList3);
     }

     void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
     {
         Bind(new ChinaStatesDA().Select(DropDownList1.SelectedValue), DropDownList2);
         Bind(new ChinaStatesDA().Select(DropDownList2.SelectedValue), DropDownList3);
     }
     //绑定方法
     public void Bind(List<ChinaStates> list, DropDownList dw)
     {
         dw.DataSource = list;
         dw.DataTextField = "AreaName";
         dw.DataValueField = "AreaCode";
         dw.DataBind();
     }

方法二：

创建三个下拉列表框：

 省：<asp:DropDownList ID="DropDownListsheng" runat="server" OnSelectedIndexChanged="DropDownListsheng_SelectedIndexChanged" AutoPostBack="True"></asp:DropDownList>
 市：<asp:DropDownList ID="DropDownListshi" runat="server" OnSelectedIndexChanged="DropDownListshi_SelectedIndexChanged" AutoPostBack="True"></asp:DropDownList>
 区：<asp:DropDownList ID="DropDownListqu" runat="server" AutoPostBack="True"></asp:DropDownList>

CS：

※DropDownList.Items.Clear(); 每调用一次填充方法就需要请空一下，否则数据会追加

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            sheng();
            shi();
            qu();
        }
    }
    public void sheng()//填充省
    {
        List<ChinaStates> listsheng = new ChinaStatesDA().Select("");
        foreach (ChinaStates cssheng in listsheng)
        {
            ListItem lisheng = new ListItem(cssheng.AreaName, cssheng.AreaCode);
            DropDownListsheng.Items.Add(lisheng);
        }
    }
    public void shi()//填充市
    {

        List<ChinaStates> listshi = new ChinaStatesDA().Select(DropDownListsheng.SelectedValue);
        foreach (ChinaStates csshi in listshi)
        {
            ListItem lishi = new ListItem(csshi.AreaName, csshi.AreaCode);
            DropDownListshi.Items.Add(lishi);
        }
    }
    public void qu()//填充区
    {

        List<ChinaStates> listqu = new ChinaStatesDA().Select(DropDownListshi.SelectedValue);
        foreach (ChinaStates csqu in listqu)
        {
            ListItem liqu = new ListItem(csqu.AreaName, csqu.AreaCode);
            DropDownListqu.Items.Add(liqu);
        }

    }
    protected void DropDownListsheng_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownListshi.Items.Clear();
        DropDownListqu.Items.Clear();
        shi();
        qu();
    }
    protected void DropDownListshi_SelectedIndexChanged(object sender, EventArgs e)
    {
        DropDownListqu.Items.Clear();
        qu();
    }