拼合父/子層次

Question

我想了解這裏的一個概念：

從對象結構像

class Parent 
{ 
    public string ParentID { get; set; } 
    public List<Child> Children { get; set; } 
} 

class Child 
{ 
    public string ChildID { get; set; } 
} 

假設完全填充的父對象，我想用的LINQ到XML獲取以下Xml輸出：

<Mappings> 
    <Mapping ID='ParentID1' ChildID='ChildID1'> 
    <Mapping ID='ParentID1' ChildID='ChildID2'> 
</Mappings> 

如何展開嵌套的原始對象以獲取此映射列表？

EDIT

實施例與父如：

ParentID = 'Parent1', Children = new [] { "Child1", "Child2", "Child3" } 

我期待3個映射：

<Mapping ID='Parent1' ChildID='Child1' /> 
<Mapping ID='Parent1' ChildID='Child2' /> 
<Mapping ID='Parent1' ChildID='Child3' /> 

Answer 1

EDIT

下面的代碼將扁平化層級：

var list = new List<Parent> 
{ 
    new Parent 
    { 
     ParentID = "parentID1", 
     Children = new List<Child> {new Child {ChildID = "childID1"}, new Child {ChildID = "childID2"}} 
    }, 
    new Parent 
    { 
     ParentID = "parentID2", 
     Children = new List<Child> {new Child {ChildID = "childID3"}, new Child {ChildID = "childID4"}} 
    } 
}; 

IEnumerable<XElement> list1 = (from parent in list 
    from child in parent.Children 
    select 
     new XElement("Mapping", new XAttribute("ID", parent.ParentID), 
      new XAttribute("ChildID", child.ChildID))); 

string @join = string.Join(Environment.NewLine, list1); 

輸出：

<Mapping ID="parentID1" ChildID="childID1" /> 
<Mapping ID="parentID1" ChildID="childID2" /> 
<Mapping ID="parentID2" ChildID="childID3" /> 
<Mapping ID="parentID2" ChildID="childID4" /> 

---

下面是關於如何實現它的一個例子：

注：這是不行的，它會產生一個異常說'重複屬性'

List<Parent> list = new List<Parent> 
{ 
    new Parent() {ParentID = "parentID1", Children = new List<Child>() {new Child() {ChildID = "childID1"},new Child() {ChildID = "childID2"}}}, 
    new Parent() {ParentID = "parentID2", Children = new List<Child>() {new Child() {ChildID = "childID3"},new Child() {ChildID = "childID4"}}} 
    }; 
IEnumerable<string> enumerable = xElements.Select(s => s.ToString()); 


IEnumerable<XElement> xElements = list.Select(s => new XElement("Mapping", new XAttribute("ID", s.ParentID), s.Children.Select(t => new XAttribute("ChildID", t.ChildID)))); 
IEnumerable<string> enumerable = xElements.Select(s => s.ToString()); 
var @join = string.Join(Environment.NewLine, enumerable); 

這人會因爲它會使用的Select使用當前對象的索引過載：

var list = new List<Parent> 
{ 
    new Parent 
    { 
     ParentID = "parentID1", 
     Children = new List<Child> {new Child {ChildID = "childID1"}, new Child {ChildID = "childID2"}} 
    }, 
    new Parent 
    { 
     ParentID = "parentID2", 
     Children = new List<Child> {new Child {ChildID = "childID3"}, new Child {ChildID = "childID4"}} 
    } 
}; 

IEnumerable<XElement> xElements = 
    list.Select(
     s => 
      new XElement("Mapping", new XAttribute("ID", s.ParentID), 
       s.Children.Select((t, u) => new XAttribute(string.Format("ChildID_{0}", u), t.ChildID)))); 
var @join = string.Join(Environment.NewLine,xElements); 

結果：不是你已經期待了吧？

<Mapping ID="parentID1" ChildID_0="childID1" ChildID_1="childID2" /> 
<Mapping ID="parentID2" ChildID_0="childID3" ChildID_1="childID4" /> 

爲什麼我使用這個過載？

因爲父母有一個兒童的列表，而第一個代碼將與一個孩子一起工作，它不會與他們中的許多人。

結論：

不知道關於你想達到什麼目的，

你爲什麼不只是保持你的對象的結構，因爲它是目前？