遞歸，就是有去有回，自己調用自己。

 1 public partial class SiteMaster : MasterPage
 2     {
 3         public DataSet list = null;
 4 
 5         public List<TreeData> treeDatas = new List<TreeData>();
 6         string str = "";
 7         protected void Page_Load(object sender, EventArgs e)
 8         {
 
 9             if (LoginMITBz.currentUser == null)
10             {
11                 Response.Redirect("/Login/Login.aspx");
12             }
13             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;
14             list = Hy.DBSqlU.DBUtility_USA.DbHelperSQLDB_USA_MIT_MitInfo.Query(sql);
15             #region Test
16 
17             //foreach (DataRow mDr in list.Tables[0].Rows)
18             // {
19             // DataColumn mDc = list.Tables[0].Columns[0];
20             //
 
Console.WriteLine(mDr["Title"].ToString());
21             //Console.WriteLine(mDr["Url"].ToString());
22 
23             //    //foreach (DataColumn mDc in list.Tables[0].Columns)
24             //    //{
25             //    //    Console.WriteLine(mDr["Title"].ToString());
26             //    //    Console.WriteLine(mDr["Url"].ToString());
27             //    //}
28             //}
29             #endregion
30 
31             foreach (DataRow mDr in list.Tables[0].Rows)
32             {
33                 DataColumn mDc = list.Tables[0].Columns[0];
34                 TreeData tree = new TreeData();
35                 tree.TreeId = (long)mDr["TreeId"];
36                 tree.Title = mDr["Title"].ToString();
37                 tree.Url = mDr["Url"].ToString();
38                 tree.ParentId = (int)mDr["ParentID"];
39                 treeDatas.Add(tree);
40             }
41 
42            
43             var data = treeDatas.Where(a => a.ParentId == 0);
44             foreach (var item in data)
45             {
46                 str += item.Title + ":" + item.Url + "\r\n";
47                 GetNode((int)item.TreeId);
48             }
49         }
50         
51         public  void GetNode(int parentId)
52         {
53             var data = treeDatas.Where(a => a.ParentId == parentId);
54             foreach (var item in data)
55             {
56                 str += item.Title + ":" + item.Url + "\r\n";
57                 GetNode((int)item.TreeId);
58             }
59         }
60     }
61     
62 
63 
64     public class TreeData
65     {
66         public long? TreeId { get; set; }
67         public int? ParentId { get; set; }
68         public string Title { get; set; }
69         public string Url { get; set; }
70     }

C#遞歸加載樹