如何从 SOAP 响应中检索元素值

Question

I have the following SOAP response and I want to get the value from the tag element a:Year1. How can I achieve this using c#?

    <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Body>
    <GetPerformanceAndRiskByTypeCodeResponse xmlns="http://tempuri.org/">
      <GetPerformanceAndRiskByTypeCodeResult xmlns:a="http://schemas.datacontract.org/2004/07/FE.Toolkit.Services.DataContracts.ResponsiveChartingTool" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
        <IsSuccessful xmlns="http://schemas.datacontract.org/2004/07/FE.Toolkit.Services.DataContracts">false</IsSuccessful>
        <ResponseCode xmlns="http://schemas.datacontract.org/2004/07/FE.Toolkit.Services.DataContracts">0</ResponseCode>
        <ResponseMessage i:nil="true" xmlns="http://schemas.datacontract.org/2004/07/FE.Toolkit.Services.DataContracts" />
        <TotalRows xmlns="http://schemas.datacontract.org/2004/07/FE.Toolkit.Services.DataContracts">0</TotalRows>
        <a:CalendarPerformanceAs>2019-12-31T00:00:00</a:CalendarPerformanceAs>
        <a:CumulativePerformanceAs>2020-10-01T00:00:00</a:CumulativePerformanceAs>
        <a:DiscretePerformanceAs>2020-09-30T00:00:00</a:DiscretePerformanceAs>
        <a:InstrumentInformation>
          <a:InstrumentInformation>
            <a:CalendarPerformance>
              <a:IncomeBasisPriceType>2</a:IncomeBasisPriceType>
              <a:PerformanceCurrency>USD</a:PerformanceCurrency>
              <a:Year1>19.031154</a:Year1>
              <a:Year2>-13.434495</a:Year2>
              <a:Year3>23.004020</a:Year3>
              <a:Year4>-5.584117</a:Year4>
              <a:Year5>-2.882996</a:Year5>
            </a:CalendarPerformance>
          </a:InstrumentInformation>
        </a:InstrumentInformation>
        <a:RiskAs>2020-09-30T00:00:00</a:RiskAs>
      </GetPerformanceAndRiskByTypeCodeResult>
    </GetPerformanceAndRiskByTypeCodeResponse>
  </s:Body>
</s:Envelope>

I tried the following but no luck:

var str = XElement.Parse(xml.Response.XmlResponse.ToString()); 
var result = str.Element("InstrumentInformation").Element("InstrumentInformation")[0].Element("CalendarPerformance").Element("Year1").Value; 
Console.WriteLine("RESULT" + result);

The error is

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.

Answer 1

You need to deal with the namespace of the element. You can ignore it and use the local name but it is more robust to include it:

XNamespace ns = "http://schemas.datacontract.org/2004/07/FE.Toolkit.Services.DataContracts.ResponsiveChartingTool";

var y1 = str.Descendants().Elements(ns + "Year1").FirstOrDefault();