DropDownList无限级分类(灵活控制显示形式)

主要使用递归实现，数据库结构： 最终样式： 1 protected void Page_Load( object sender, EventArgs e) 2      { 3        if (!Page.IsPostBack) 4        { 5             BindDrpClass(); 6         } 7     } 8      // 绑定顶级分类 9      private void BindDrpClass() 10      { 11         Bll.Class classSystem = new Bll.Class(); 12         DataTable dt = classSystem.GetClassList("").Tables[0]; 13         ddlClass.Items.Clear(); 14         ddlClass.Items.Add(new ListItem("添加根栏目","0")); 15         DataRow[] drs = dt.Select("ParentID= " + 0); 16 17        foreach (DataRow dr in drs) 18        { 19            string classid = dr["ClassID"].ToString(); 20            string classname = dr["ClassName"].ToString(); 21            //顶级分类显示形式 22             classname = "╋" + classname; 23 24             ddlClass.Items.Add(new ListItem(classname, classid)); 25            int sonparentid = int.Parse(classid); 26            string blank = "├"; 27            //递归子分类方法 28             BindNode(sonparentid, dt, blank); 29         } 30         ddlClass.DataBind(); 31     } 32      // 绑定子分类 33      private void BindNode( int parentid, DataTable dt, string blank) 34      { 35         DataRow[] drs = dt.Select("ParentID= " + parentid); 36 37        foreach (DataRow dr in drs) 38        { 39            string classid = dr["ClassID"].ToString(); 40            string classname = dr["ClassName"].ToString(); 41 42             classname = blank + classname; 43             ddlClass.Items.Add(new ListItem(classname, classid)); 44 45            int sonparentid = int.Parse(classid); 46            string blank2 = blank + "─"; 47 48             BindNode(sonparentid, dt, blank2); 49         } 50     } 数据访问（Bll里面的classSystem方法 ） 1public DataSet GetClassList(string strWhere) 2        { 3             StringBuilder strSql = new StringBuilder(); 4             strSql.Append("select * from tb_Class "); 5            if (strWhere.Trim() != "") 6            { 7                 strSql.Append(" where " + strWhere); 8             } 9            return SqlHelper.ExecuteDataset(SqlHelper.ConnString, CommandType.Text, strSql.ToString()); 10