使用LINQ到XML獲取元素的屬性值

Question

我有以下xml，我想獲取具有屬性的節點的值。

<quiz xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="quiz.xsd"> 
    <mchoice> 
     <question>What is the capital city of Australia?</question> 
     <answer>Sydney</answer> 
     <answer correct="yes">Canberra</answer> 
     <answer>Melbourne</answer> 
     <answer>Gold Coast</answer> 
    </mchoice> 
    <mchoice> 
     <question>Launceston is the second largest city in which Australian state?</question> 
     <answer>Victoria</answer> 
     <answer>New South Wales</answer> 
     <answer correct="yes">Tasmania</answer> 
     <answer>Western Australia</answer> 
    </mchoice> 
</quiz> 


public class Question 
{ 
    public string QuestionText { get; set; } 
    public List<string> Answers { get; set; } 
    public string CorrectAnswer { get; set; } 

} 

我嘗試下面的查詢，但我在越來越空CorrectAnswer申請

var questions = from docs in _doc.Descendants("mchoice") 
         let answers = _doc.Elements("answer") 
         select new Question 
         { 
          QuestionText = docs.Element("question").Value, 
          Answers = docs.Elements("answer").Select(a => a.Value).ToList(), 
          CorrectAnswer=docs.Elements("answer").Where(x=>x.Attribute("correct").Value=="yes").Select(x=>x) 

的例外輸出

• QuestionText，什麼是澳大利亞的首都？

• 回答名錄

• CorrectAnswer堪培拉

Answer 1

嘗試改變這一行：

CorrectAnswer=docs.Elements("answer").Where(x=>x.Attribute("correct").Value=="yes").Select(x=>x) 

爲：

CorrectAnswer=docs.Elements("answer") 
    .First(x=> x.HasAttributes && x.Attribute("correct").Value=="yes") 
    .Value