的LINQ to XML查詢返回錯誤的數據

Question

我有這樣的XML

<?xml version="1.0" encoding="utf-8" ?> 
<Departments> 
<Department> 
    <id>001</id> 
    <Section> 
    <SectionId>001001</SectionId> 
    <Room> 
     <RoomID>001001001</RoomID> 
     <Owner>guest1</Owner> 
    </Room> 
    <Room> 
     <RoomID>001001002</RoomID> 
     <Owner>guest11</Owner> 
    </Room> 
    </Section> 
    <Section> 
    <SectionId>001002</SectionId> 
    <Room> 
     <RoomID>001002001</RoomID> 
     <Owner>guest2</Owner> 
    </Room> 
</Section> 
</Department> 
</Departments> 

，這是使用LINQ to XML我的代碼

var xDoc = XDocument.Load(inputUrl); 

var sections = from el in xDoc.Descendants("Department") 
         where el.Element("id").Value.Equals("001") 
         select el.Element("Section"); 

var rooms = from el in sections 
       where el.Element("SectionId").Value.Equals("001001") 
       select el.Element("Room"); 

var roomsList = (from el in rooms 
      select new Room 
      { 
       roomID = (string)el.Element("RoomID"), 
       owner = (string)el.Element("Owner") 
      }).ToList(); 

我的問題是我只在列表獲得1間房間，但我應該得到兩個。請同樣建議，如果這是使用LINQ to xml的正確方式，那麼對於LINQ我是相當新的。

Answer 1

只是表明，有很多方法可以皮膚貓：

var xDoc = XDocument.Load(@"C:\TEST\TEST.XML"); 

var depts = from e in xDoc.Descendants("Department") 
      where e.Element("id").Value.Equals("001") 
      select e; 

var sections = from e in depts.Descendants("Section") 
      where e.Element("SectionId").Value.Equals("001001") 
      select e; 

var rooms = (from e in sections.Descendants("Room") 
      select new //Room 
      { 
       ID = (string)e.Element("RoomID"), 
       Owner = (string)e.Element("Owner") 
      }).ToList(); 

Answer 2

如果你改變什麼：

select el.Element("Room"); 

到

select el.Elements("Room"); 

Answer 3

你只是在中間的查詢選擇一個房間，應該是.Elements(...)（注意尾隨s）：

 var rooms = from el in sections 
         where el.Element("SectionId").Value.Equals("001001") 
         select el.Elements("Room"); 

這同樣適用於您的section查詢。

Answer 4

變化sections和rooms查詢：

var sections = xDoc.Descendants("Department") 
        .FirstOrDefault(x => (string)x.Element("id") == "001") 
        .Elements("Section"); 

var rooms = sections.Where(x => (string)x.Element("SectionId") == "001001") 
        .Elements("Room"); 

有了這些，你會得到2個房間。

爲什麼不是你的代碼工作？

1. select el.Element("Section")內Department只選擇第一section元素 - 你永遠無法從section與id == "001002"
2. select el.Element("Room")在rooms查詢來獲取返回房間只從每一個匹配部分的第一個房間。

您可以更改Element到Elements，並增加額外SelectMany(x => x)通話，讓您的基於語法的查詢工作：

var sections = from el in xDoc.Descendants("Department") 
       where el.Element("id").Value.Equals("001") 
       select el.Elements("Section"); 

var rooms = from el in sections.SelectMany(x => x) 
      where el.Element("SectionId").Value.Equals("001001") 
      select el.Elements("Room"); 

var roomsList = (from el in rooms.SelectMany(x => x) 
        select new 
        { 
         roomID = (string)el.Element("RoomID"), 
         owner = (string)el.Element("Owner") 
        }).ToList(); 

Answer 5

作爲替代其他的答案，你可以使用Extensions.XPathSelectElements Method (XNode, String)（請確保您在using System.Xml.XPath指令添加到您的文件的頂部）：

string 
    departmentId = "001", 
    sectionId = "001001"; 
var xDoc = XDocument.Load(inputUrl); 
var rooms = xDoc.XPathSelectElements(
    String.Format(
     "//Department[id={0}]/Section[SectionId={1}]/Room", 
     departmentId, 
     sectionId)) 
    .Select(el => new Room 
    { 
     roomID = (string)el.Element("RoomID"), 
     owner = (string)el.Element("Owner") 
    }).ToList(); 

它自己喜好的問題。我覺得這篇文章寫得更簡短，更易於閱讀。