LINQ to XML查詢。 獲取元素屬性

Question

由於Cannot convert lambda expression to delegate type因此無法獲取answer屬性。 這些是我的課程和查詢：

var file = XDocument.Load("QuestionsTest.xml");
var questions = from answers in file.Root.Elements("Question").Elements("Answers").Elements("Answer")
                        select new Answer
                        {
                            Text = (string)answers,
                            Correct = (string)answers.Elements("Answer").Single(answer=>(string)answer.Attribute("Correct"))
                        };

public class Answer
{
    public int AnswerID { get; set; }
    public string Text { get; set; }
    public string Correct { get; set; }
    public int Stats { get; set; }

    public int QuestionID { get; set; }
}

public class Question
{
    public virtual List<Answer> Answers { get; set; }
}

我的XML如下所示：

<?xml version="1.0" encoding="utf-8" ?>
<Questions Subject="ADO.NET">
  <Question  NumberOfAnswers="1">
    <Text>Which class should you use to manage multiple tables and relationships among them?</Text>
    <Answers>
      <Answer>DataRow</Answer>
      <Answer>DataView</Answer>
      <Answer>DataTable</Answer>
      <Answer Correct="Yes">DataSet</Answer>
    </Answers>
 </Question>
  </Questions>

如何獲得答案的屬性？

Answer 1

Enumerable.Single接受Func<T,bool>委托，該委托應返回布爾值。 您正在傳遞返回XAttribute值的委托。 您應該將屬性值與Yes字符串進行比較 ，以返回布爾結果：

Single(answer => (string)answer.Attribute("Correct") == "Yes")

這將解決您的錯誤。 但我認為您也應該更改查詢的邏輯。 首先更改Answer類，然后將Correct屬性設置為布爾值：

public class Answer
{
    public int AnswerID { get; set; }
    public string Text { get; set; }
    public bool IsCorrect { get; set; }
    public int Stats { get; set; }
    public int QuestionID { get; set; }
}

查詢應如下所示：

var xdoc = XDocument.Load("QuestionsTest.xml");
var questions =
      from q in xdoc.Descendants("Question")
      select new Question {
          Answers = (from a in q.Descendants("Answer")
                     select new Answer {
                        Text = (string)a,
                        IsCorrect = (string)a.Attribute("Correct") == "Yes"
                    }).ToList()
      };

Answer 2

var questions = from answers in 
    file.Root.Elements("Question").Elements("Answers").Elements("Answer")
    select new Answer
    {
        Text = (string)answers,
        Correct = (string)answers.Attribute("Correct")
    };