【轉】C#遞迴查詢

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轉自：http://www.cnblogs.com/no27/p/6673893.html

一、sql

--構造測試資料： 只作示範用 CREATE TABLE [dbo].[Tim_LinqTable]( [Id] int PRIMARY KEY IDENTITY(1,1) NOT NULL, [Name] [varchar](50) NOT NULL, [Parent] int NOT NULL, ) GO    INSERT INTO [Tim_LinqTable]   SELECT ‘A‘,0 UNION ALL SELECT ‘A1‘,1 UNION ALL SELECT ‘A2‘,1 UNION ALL SELECT ‘B1‘,2 UNION ALL SELECT ‘B2‘,3 UNION ALL SELECT ‘C1‘,4 UNION ALL SELECT ‘C2‘,4 UNION ALL SELECT ‘D1‘,5 UNION ALL SELECT ‘D2‘,5 UNION ALL SELECT ‘D3‘,5  GO    WITH temp AS ( SELECT * FROM [Tim_LinqTable]  WHERE Parent = 3 UNION ALL SELECT m.* FROM [Tim_LinqTable]  AS m INNER JOIN temp AS child ON m.Parent = child.Id ) SELECT * FROM temp GO    --查詢 Parent=3 的所有子資料結果如下: Id          Name                                               Parent ----------- -------------------------------------------------- ----------- 5           B2                                                 3 8           D1                                                 5 9           D2                                                 5 10          D3                                                 5    (4 row(s) affected) 

二、實現

//好，下邊來看看用C#怎麼實現上邊的SQL語句吧： void Main() {      var query=GetSonID(3);      Console.WriteLine("Id\tName\tParent");      query.ToList().ForEach(q=>Console.WriteLine("{0}\t{1}\t{2}",q.Id,q.Name,q.Parent));      /*        Id       Name       Parent        5        B2         3        8        D1         5        9        D2         5            10        D3         5     */ } public IEnumerable<Tim_LinqTable> GetSonID(int p_id) {     var query = from c in this.Tim_LinqTables            where c.Parent  == p_id            select c;                 return  query.ToList().Concat(query.ToList().SelectMany(t => GetSonID(t.Id)));               } 

或者：

public static List<db_userinfo> findallchildren(int parentid){    var list = (from c in ctdt.db_userinfo                where c.parent_id == parentid                select c).ToList();    List<db_userinfo> tmpList = new List<db_userinfo>(list);    foreach (db_userinfo single in temp)    {        List<db_userinfo> tmpChildren = findallchildren(single.user_id);        if (single.PB_Level == 1)//如果迴圈到最後一層退出        {            return list;        }        if (tmpChildren.Count != 0)        {            list.AddRange(tmpChildren);        }    }    return list;}

 

【轉】C#遞迴查詢