DropDownList 三级 联动 (转)

本文转载地址: http://blog.csdn.net/wxd_860825/article/details/4563368

前台代码:

        <div style="float: left" mce_style="float: left">
            <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                <ContentTemplate>
                    <asp:DropDownList ID="DropDownList1" runat="server" Width="98px" AutoPostBack="true"
                        OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" OnTextChanged="DropDownList1_SelectedIndexChanged">
                    </asp:DropDownList>
                    <asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="true" Width="168px"
                        OnSelectedIndexChanged="DropDownList2_SelectedIndexChanged">
                    </asp:DropDownList>
                    <asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="true" Width="168px">
                    </asp:DropDownList>
                </ContentTemplate>
            </asp:UpdatePanel>
        </div>
        <div style="float: left" mce_style="float: left">
            &nbsp;</div>

后台代码：

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            //绑定第一个下拉框
            Dd1DataBind();
            //显示第一个下拉框对应的第二个下拉框的内容
            Dd2DataBind();
            //显示第二个下拉框对应的第三个下拉框的内容
            Dd3DataBind();
        }
    }
    //当下拉框改变时，显示相应的内容
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        Dd2DataBind();
        Dd3DataBind();
    }
    //当下拉框改变时，显示相应的内容
    protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        Dd3DataBind();
    }
    //DropDownList1
    public void Dd1DataBind()
    {
        string sqlStr = "Select TypeID,TypeName From a ";
        FillDropList(sqlStr, DropDownList1);
    }
    //DropDownList2
    public void Dd2DataBind()
    {
        int PreID = Convert.ToInt32(DropDownList1.SelectedValue);
        string sqlStr1 = "Select ID,name From b Where TypeID=' " + PreID.ToString() + "'";
        FillDropList(sqlStr1, DropDownList2);
    }
    //DropDownList3
    public void Dd3DataBind()
    {
        int PreID = Convert.ToInt32(DropDownList2.SelectedValue);
        string sqlStr2 = "Select IDcun,name From c Where ID=' " + PreID.ToString() + "'";
        FillDropList(sqlStr2, DropDownList3);
    }
    //绑定方法
    public void FillDropList(string SQLString, DropDownList drp)
    {
        SqlConnection connection = new SqlConnection("database=wxd;server=(local);uid=sa;pwd=sa");
        SqlCommand cmd = new SqlCommand(SQLString, connection);
        SqlDataAdapter sda = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        sda.Fill(ds, "DropList");
        drp.DataSource = ds.Tables["DropList"].DefaultView;
        drp.DataTextField = ds.Tables["DropList"].Columns[1].ColumnName;
        drp.DataValueField = ds.Tables["DropList"].Columns[0].ColumnName;
        drp.DataBind();
    }