使用Linq獲取兒童記錄

Question

這是我第一次聽到LINQ，我不知道它。請對我溫柔。

我有這套數據。

+---------+--------+---------------+ 
| RadioID | NodeID | SourceRadioID | 
+---------+--------+---------------+ 
| R0  |  1 |    | 
| R1  |  1 |    | 
| R2  |  1 |    | 
| R3  |  1 |    | 
| R4  |  1 |    | 
| R5  |  2 |    | 
| R6  |  2 |    | 
| R7  |  2 | R0   | 
| R8  |  2 |    | 
| R9  |  2 |    | 
| R10  |  11 |    | 
| R11  |  11 | R9   | 
| R12  |  11 |    | 
| R13  |  11 |    | 
+---------+--------+---------------+ 

我需要做的是寫一個返回的NodeID列表的方法。例如，

List<int> dependentNode = GetChildNode(1); // int ParentNode 

我的預期結果是NodeID：2 and 11。

NodeID = 2是因爲有一個RadioID = R7連接到RadioID = R0屬於NodeID = 1。也包括

NodeID = 11因爲RadioID = R11連接到Radio = R9屬於NodeID = 2（也被連接到NodeID = 1）。

我查找此文章，但我總是得到StackOverFlowException

• ​​

下面是完整的代碼：

public class RadioEntity 
{ 
    public string RadioID { get; set; } 
    public int NodeID { get; set; } 
    public string SourceRadioID { get; set; } 
} 

public class SampleDemo 
{ 
    public void SampleMethod() 
    { 

     Func<int, int,List<int>> GetChildNode = null; 
     GetChildNode = (x, y) => 
      { 
       return (from _x in GetRadio() 
         where (GetRadio().Where(i => i.NodeID == x).Select(i => i.RadioID)).Contains(_x.RadioID) 
         from _y in new[] { _x.NodeID }.Union(GetChildNode(_x.NodeID, y + 1)) 
         select _y).ToList<int>(); 
      }; 

     var _res = GetChildNode(1, 0); 

    } 

    public List<RadioEntity> GetRadio() 
    { 
     List<RadioEntity> _returnVal = new List<RadioEntity>(); 
     _returnVal.Add(new RadioEntity() { RadioID = "R0", NodeID = 1, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R1", NodeID = 1, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R2", NodeID = 1, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R3", NodeID = 1, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R4", NodeID = 1, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R5", NodeID = 2, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R6", NodeID = 2, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R7", NodeID = 2, SourceRadioID = "R0" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R8", NodeID = 2, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R9", NodeID = 2, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R10", NodeID = 11, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R11", NodeID = 11, SourceRadioID = "R9" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R12", NodeID = 11, SourceRadioID = "" }); 
     _returnVal.Add(new RadioEntity() { RadioID = "R13", NodeID = 11, SourceRadioID = "" }); 

     return _returnVal; 
    } 

} 

，如果有更好的方法來做到這一點你可以建議。對不起，新手在這裏。

Answer 1

如果你是新手，不要太巧與遞歸和lambda表達式。

public List<int> GetChildren(int id) 
    { 
     var nodes = GetRadio(); 
     var parent = nodes.Single(n => n.NodeID == id); 
     var children = nodes.Where(n => n.SourceRadioID == parent.RadioID).Select(n => n.NodeID); 

     return children.Union(children.SelectMany(GetChildren)).ToList(); 
    } 

---

更新1

public List<int> GetChildren(int id) 
{ 
    IEnumerable<RadioEntity> parent = GetRadio().Where(x => x.NodeID == id); 
    IEnumerable<int> children = (
            from r in GetRadio() 
            where parent.Select(x=>x.RadioID) 
               .Contains(r.SourceRadioID) 
            select r 
           ).Select(n => n.NodeID); 

    return children.Union(children.SelectMany(GetChildren)).ToList(); 
}