dropdownlist 实现无限级树形菜单

private void BindDrpClass()
    {
        //获得所有数据列表
        DataTable dt = mh.returnds_bysting("select * from TB_SupplyType ").Tables [0];
        ddl . Items.Clear();
        ddl.Items.Add(new ListItem("选择类别", "0"));
        DataRow[] drs = dt.Select("s_Sid= " + 0);

        foreach (DataRow dr in drs)
        {
            string classid = dr["s_Id"].ToString();
            string classname = dr["s_Title"].ToString();
            //顶级分类显示形式
            classname = "" + classname;

            ddl.Items.Add(new ListItem(classname, classid));
            int sonparentid = int.Parse(classid);
            string blank = "　　　";
            //递归子分类方法
            BindNode(sonparentid, dt, blank);
        }
        ddl.DataBind();
    }
    private void BindNode(int parentid, DataTable dt, string blank)
    {
        DataRow[] drs = dt.Select("s_Sid= " + parentid);

        foreach (DataRow dr in drs)
        {
            string classid = dr["s_Id"].ToString();
            string classname = dr["s_Title"].ToString();

            classname = blank + classname;
            ddl.Items.Add(new ListItem(classname, classid));

            int sonparentid = int.Parse(classid);
            string blank2 = blank + "-";
            BindNode(sonparentid, dt, blank2);
        }
    }

虽然能实现无限级分类，但是样式有点逊色，有兴趣的朋友可以加个css 控制一下