C# 读取和检索xml元素

我需要读取xml文件中的所有嵌套元素。下面是节目。在下面的程序中，我可以得到问题和答案的值，但不能得到子问题答案/问题和子问题答案/答案的值。有人能告诉我我的程序出了什么问题吗

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);
                    }


            }

XmlDocument XmlDocument=new XmlDocument（）；
var fataQuestionnaire=@”
你的财富来源是什么？
我是意大利人
你的职业和雇主的名字是什么？
贝斯廷维斯特
你在中国有生意或住所吗？
对
你在阿尔巴尼亚境外住了多久
五年
你定期回阿尔巴尼亚吗
对
多久一次？
每年
你在阿尔巴尼亚有家人吗？
对
家庭关系？
我父母住在那里
你与阿尔巴尼亚政府有联系吗？
对
结社性质
我是前部长
你从阿尔巴尼亚寄钱还是收到钱？
对
多久一次，为什么？
每个月我都要和父母住在一起。
";
XmlTextReader=新的XmlTextReader（新的StringReader（fataQuestionnaire））；
加载（读卡器）；
XmlElement xmlRoot=xmlDocument.DocumentElement；
if（xmlRoot！=null）
{
XmlNodeList xnlNodes=xmlRoot.SelectNodes（“/fatcaQuestionly/QuestionAnswers/QuestionAnswers”）；
string questionanswer=string.Empty；
if（xnlNodes！=null）
foreach（xnlNodes中的XmlNode xndNode）
{
if（xndNode[“问题”]！=null）
questionanswer=（xndNode[“问题”].InnerText）；
如果（xndNode[“应答”]！=null）
questionanswer=（xndNode[“答案”].InnerText）；
if（xndNode[“子问题答案/问题”]！=null）
questionanswer=（xndNode[“子问题答案/问题”]。InnerText）；
if（xndNode[“子问题答案/答案”]！=null）
问题答案=（xndNode[“子问题答案/答案”]。InnerText）；
}
}

索引器不支持XPath语法。您可以通过以下方式进行修复：

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

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

---

另一个选项：使用XDocument和Linq代替XmlDocument

加载xml:

XDocument doc = XDocument.Parse(fataQuestionnaire);

示例用法：

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");
}

或：

结果:

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.

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.

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.