C#递归加载树

递归，就是有去有回，自己调用自己。

public partial class SiteMaster : MasterPage
    {
        public DataSet list = null;

        public List<TreeData> treeDatas = new List<TreeData>();
        string str = "";
        protected void Page_Load(object sender, EventArgs e)
        {
            if (LoginMITBz.currentUser == null)
            {
                Response.Redirect("/Login/Login.aspx");
            }
            string sql = "SELECT a.Title,a.TreeId,a.Url,a.ParentID,a.ParentPath FROM dbo.M_Tree a INNER JOIN dbo.M_Permissions b ON a.TreeId = b.TreeId WHERE b.UserId=" + LoginMITBz.currentUser.UserId;
            list = Hy.DBSqlU.DBUtility_USA.DbHelperSQLDB_USA_MIT_MitInfo.Query(sql);
            #region Test

            //foreach (DataRow mDr in list.Tables[0].Rows)
            // {
            // DataColumn mDc = list.Tables[0].Columns[0];
            //Console.WriteLine(mDr["Title"].ToString());
            //Console.WriteLine(mDr["Url"].ToString());

            //    //foreach (DataColumn mDc in list.Tables[0].Columns)
            //    //{
            //    //    Console.WriteLine(mDr["Title"].ToString());
            //    //    Console.WriteLine(mDr["Url"].ToString());
            //    //}
            //}
            #endregion

            foreach (DataRow mDr in list.Tables[0].Rows)
            {
                DataColumn mDc = list.Tables[0].Columns[0];
                TreeData tree = new TreeData();
                tree.TreeId = (long)mDr["TreeId"];
                tree.Title = mDr["Title"].ToString();
                tree.Url = mDr["Url"].ToString();
                tree.ParentId = (int)mDr["ParentID"];
                treeDatas.Add(tree);
            }

           
            var data = treeDatas.Where(a => a.ParentId == 0);
            foreach (var item in data)
            {
                str += item.Title + ":" + item.Url + "
";
                GetNode((int)item.TreeId);
            }
        }
        
        public  void GetNode(int parentId)
        {
            var data = treeDatas.Where(a => a.ParentId == parentId);
            foreach (var item in data)
            {
                str += item.Title + ":" + item.Url + "
";
                GetNode((int)item.TreeId);
            }
        }
    }
    


    public class TreeData
    {
        public long? TreeId { get; set; }
        public int? ParentId { get; set; }
        public string Title { get; set; }
        public string Url { get; set; }
    }