Parse XML response from service asp.net

Question

I am trying to integrate a web service with my project. The web service returns an XML response:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" 
                   xmlns:ns1="http://www.tpg.ua/" 
                   xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
                   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
                   xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" 
                   SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
    <SOAP-ENV:Body>
        <ns1:getCitiesResponse>
            <return xsi:type="xsd:string">
                [
                    {
                        "cityTitle": "Тирана",
                        "countryId": "7",
                        "cityId": "2493",
                        "IATA": "TIA"
                    },
                    {
                        "cityTitle": "Ла-Романа",
                        "countryId": "48",
                        "cityId": "1280",
                        "IATA": "LRM"
                    },
                    {
                        "cityTitle": "Херсон",
                        "countryId": "145",
                        "cityId": "2719",
                        "IATA": "KHE"
                    },
                    {
                        "cityTitle": "Шарм",
                        "countryId": "49",
                        "cityId": "2851",
                        "IATA": "SSH"
                    }
                ]
            </return>
        </ns1:getCitiesResponse>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

I am trying to parse that response. I want to get the cityId and the countryId

XmlDocument listXML = new XmlDocument();
listXML.LoadXml(response);

string baseNode = @"return/";

XmlNode item1 = listXML.SelectSingleNode(baseNode + "countryId"); 
XmlNode item2 = listXML.SelectSingleNode(baseNode + "cityId");

string s = item1.InnerText.ToString();
string s1 = item2.InnerText.ToString();

But it is null; what should I do?

Answer 1

The return element of your SOAP response contains a JSON string, so you cannot use XmlDocument and an XPath query to extract data from that.

You need to query the JSON data with a JSON deserializer, for example I have used JSON.NET in this example - you can add this to your project by installing the NuGet package Newtonsoft.Json.

So there are two steps here - firstly extract the content of the return element from the XML response. I use XDocument rather than XmlDocument as you have used, as XDocument is a more modern API and plays nicer with modern language features such as Linq.

Second step is to deserialise the JSON content, and extract the content into variables.

var xDoc = XDocument.Parse(response);
var returnJson = xDoc.Descendants("return")
    .Single()
    .Value;

var cities = JArray.Parse(returnJson);
foreach (var city in cities)
{
    var cityId = city["cityId"].Value<string>();
    var countryId = city["countryId"].Value<string>();
}