讀取和檢索xml元素

Question

我需要讀取我的xml文件中的所有嵌套元素。以下是該計劃。在下面的程序中，我可以獲得問題和答案的值，但不能用於SubQuestionAnswer/Question和SubQuestionAnswer/Answer。有人能告訴我什麼是我的程序錯誤

XmlDocument xmlDocument = new XmlDocument(); 

      var fataQuestionnaire = @"<?xml version=""1.0"" encoding=""UTF-16""?> 
       <FatcaQuestionnaire xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"" xmlns:xsd=""http://www.w3.org/2001/XMLSchema""> 
        <QuestionAnswers> 
        <QuestionAnswer> 
         <Question>What is your source of wealth?</Question> 
         <Answer>I am italian </Answer> 
        </QuestionAnswer> 
        <QuestionAnswer> 
         <Question>What is your occupation and name of employer?</Question> 
         <Answer>Bestinvest</Answer> 
        </QuestionAnswer> 
        <QuestionAnswer> 
         <Question>Do you have a business or residence in?</Question> 
         <Answer>Yes</Answer> 
        </QuestionAnswer> 
        <QuestionAnswer> 
         <Question>How long have you lived outside of Albania</Question> 
         <Answer>5 years</Answer> 
        </QuestionAnswer> 
        <QuestionAnswer> 
         <Question>Do you return to Albania on a regular basis</Question> 
         <Answer>Yes</Answer> 
         <SubQuestionAnswer> 
         <Question>How frequently?</Question> 
         <Answer>every year</Answer> 
         </SubQuestionAnswer> 
        </QuestionAnswer> 
        <QuestionAnswer> 
         <Question>Do you have family in Albania?</Question> 
         <Answer>Yes</Answer> 
         <SubQuestionAnswer> 
         <Question>Family relationship?</Question> 
         <Answer>My parents lives there</Answer> 
         </SubQuestionAnswer> 
        </QuestionAnswer> 
        <QuestionAnswer> 
         <Question>Are you connected to the government of Albania?</Question> 
         <Answer>Yes</Answer> 
         <SubQuestionAnswer> 
         <Question>Nature of association</Question> 
         <Answer>I was an ex minister</Answer> 
         </SubQuestionAnswer> 
        </QuestionAnswer> 
        <QuestionAnswer> 
         <Question>Do you send or receive money from Albania?</Question> 
         <Answer>Yes</Answer> 
         <SubQuestionAnswer> 
         <Question>How often and why?</Question> 
         <Answer>Every month for my parents to live with.</Answer> 
         </SubQuestionAnswer> 
        </QuestionAnswer> 
        </QuestionAnswers> 
       </FatcaQuestionnaire>"; 

      XmlTextReader reader = new XmlTextReader(new StringReader(fataQuestionnaire)); 


      xmlDocument.Load(reader); 

      XmlElement xmlRoot = xmlDocument.DocumentElement; 
      if (xmlRoot != null) 
      { 
       XmlNodeList xnlNodes = xmlRoot.SelectNodes("/FatcaQuestionnaire/QuestionAnswers/QuestionAnswer"); 
       string questionanswer =string.Empty; 


       if (xnlNodes != null) 
        foreach (XmlNode xndNode in xnlNodes) 
        { 
         if (xndNode["Question"] != null) 
          questionanswer = (xndNode["Question"].InnerText); 

         if (xndNode["Answer"] != null) 
          questionanswer = (xndNode["Answer"].InnerText); 


         if (xndNode["SubQuestionAnswer/Question"] != null) 
          questionanswer = (xndNode["SubQuestionAnswer/Question"].InnerText); 

         if (xndNode["SubQuestionAnswer/Answer"] != null) 
          questionanswer = (xndNode["SubQuestionAnswer/Answer"].InnerText); 
        } 


      } 

Answer 1

索引器不支持XPath語法。你可以這樣修復：

if (xndNode["SubQuestionAnswer"] != null) 
{ 
    if (xndNode["SubQuestionAnswer"]["Question"] != null) 
     questionanswer = (xndNode["SubQuestionAnswer"]["Question"].InnerText); 

    if (xndNode["SubQuestionAnswer"]["Answer"] != null) 
     questionanswer = (xndNode["SubQuestionAnswer"]["Answer"].InnerText); 
} 

Answer 2

另一種選擇：代替XmlDocument使用XDocument和Linq。

裝載XML：

XDocument doc = XDocument.Parse(fataQuestionnaire); 

例如使用：

List<KeyValuePair<string,string>> allQuestionAnswers = doc.Descendants("QuestionAnswer").Union(doc.Descendants("SubQuestionAnswer")) 
    .Select(qa=>new KeyValuePair<string,string>(qa.Element("Question").Value, qa.Element("Answer").Value)).ToList(); 

foreach (var pair in allQuestionAnswers) 
{ 
    Console.WriteLine("Q: " + pair.Key +"\nA: " + pair.Value + "\n"); 
} 

結果：

Q: What is your occupation and name of employer? 
A: Bestinvest 

Q: Do you have a business or residence in? 
A: Yes 

Q: How long have you lived outside of Albania 
A: 5 years 

Q: Do you return to Albania on a regular basis 
A: Yes 

Q: Do you have family in Albania? 
A: Yes 

Q: Are you connected to the government of Albania? 
A: Yes 

Q: Do you send or receive money from Albania? 
A: Yes 

Q: How frequently? 
A: every year 

Q: Family relationship? 
A: My parents lives there 

Q: Nature of association 
A: I was an ex minister 

Q: How often and why? 
A: Every month for my parents to live with. 

或：

doc.Descendants("QuestionAnswer").ToList().ForEach(qa => 
{ 
    Console.WriteLine("Q: " + qa.Element("Question").Value + "\nA: " + qa.Element("Answer").Value); 
    var sqa = qa.Element("SubQuestionAnswer"); 
    if (sqa != null) 
    { 
     Console.WriteLine("\tQ: " + sqa.Element("Question").Value + "\n\tA: " + sqa.Element("Answer").Value); 
    } 
    Console.WriteLine(); 
}); 

結果：

Q: What is your source of wealth? 
A: I am italian 

Q: What is your occupation and name of employer? 
A: Bestinvest 

Q: Do you have a business or residence in? 
A: Yes 

Q: How long have you lived outside of Albania 
A: 5 years 

Q: Do you return to Albania on a regular basis 
A: Yes 
    Q: How frequently? 
    A: every year 

Q: Do you have family in Albania? 
A: Yes 
    Q: Family relationship? 
    A: My parents lives there 

Q: Are you connected to the government of Albania? 
A: Yes 
    Q: Nature of association 
    A: I was an ex minister 

Q: Do you send or receive money from Albania? 
A: Yes 
    Q: How often and why? 
    A: Every month for my parents to live with.