展平父/子层次结构[关闭]

Question

我在这里试图理解一个概念：

从一个像这样的对象结构

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

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

假设一个完全填充的父对象，我想使用 Linq to Xml 来获得以下 Xml 输出：

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

如何展开嵌套的原始对象以获得此映射列表？

编辑

以父母为例，例如：

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

我期待 3 个映射：

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

Answer 1

编辑

以下代码将扁平化层次结构：

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);

输出：

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

---

这是一个关于如何实现它的示例：

注意：这不起作用，它会生成一个异常，说“重复属性”

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);

这是因为它会使用Select 的重载，它使用当前对象的索引：

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);

结果：不是你所期待的，对吧？

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

为什么我使用了这个重载？

因为父级有一个子级列表，而第一个代码适用于一个子级，但不适用于许多子级。

结论：

不确定您要达到的目标，

为什么不保持对象的结构不变呢？