How to get a specific part of the data from a rest webservice responce?

Question

im new in rest webservices and i try to understand how to work with them.

i define a http get request in C# like this:

static string HttpGet(string url)
        {
            HttpWebRequest req = WebRequest.Create(url)
                                 as HttpWebRequest;
            string result = null;
            using (HttpWebResponse resp = req.GetResponse()
                                          as HttpWebResponse)
            {
                StreamReader reader =
                    new StreamReader(resp.GetResponseStream());
                result = reader.ReadToEnd();
            }
            return result;
        }

then i use HttpGet in a button to get xml data from THIS weather webservice (i put the txtOut to findout that my code work).

private void btnGet_Click(object sender, RoutedEventArgs e)
        {
            string test = HttpGet("http://api.openweathermap.org/data/2.5/weather?q=London&mode=xml");

            txtOut.Text = test;
        }

its geting the whole xml from sending get request to that url: http://api.openweathermap.org/data/2.5/weather?q=London&mode=xml

so my question is how can i save specific part of that xml in a variable? like minimum temperature that is in kalvin so i can convert it to Fahrenheit or Celsius.

help me please.

Answer 1

You api also returns json, so you can use it like below (using Json.Net)

using (WebClient wc = new Webclient())
{
    var json = wc.DownloadString("http://api.openweathermap.org/data/2.5/weather?q=London&mode=json");
    var obj = JsonConvert.DeserializeObject<OpenWeatherMap.Root>(json);
}

---

public class OpenWeatherMap
{
    public class Coord
    {
        public double lon { get; set; }
        public double lat { get; set; }
    }

    public class Sys
    {
        public int type { get; set; }
        public int id { get; set; }
        public double message { get; set; }
        public string country { get; set; }
        public int sunrise { get; set; }
        public int sunset { get; set; }
    }

    public class Weather
    {
        public int id { get; set; }
        public string main { get; set; }
        public string description { get; set; }
        public string icon { get; set; }
    }

    public class Main
    {
        public double temp { get; set; }
        public int humidity { get; set; }
        public double pressure { get; set; }
        public double temp_min { get; set; }
        public double temp_max { get; set; }
    }

    public class Wind
    {
        public double speed { get; set; }
        public double gust { get; set; }
        public int deg { get; set; }
    }



    public class Clouds
    {
        public int all { get; set; }
    }

    public class Root
    {
        public Coord coord { get; set; }
        public Sys sys { get; set; }
        public List<Weather> weather { get; set; }
        public string @base { get; set; }
        public Main main { get; set; }
        public Wind wind { get; set; }
        public Dictionary<string,double> rain { get; set; }
        public Clouds clouds { get; set; }
        public int dt { get; set; }
        public int id { get; set; }
        public string name { get; set; }
        public int cod { get; set; }
    }
}

If you insist on using xml then you can use Linq2Xml + XPath

var xDoc = XDocument.Load("http://api.openweathermap.org/data/2.5/weather?q=London&mode=xml");

var windSpeed  = (double)xDoc.XPathSelectElement("//wind/speed").Attribute("value");

or

var temp = (double)xDoc.Root.Element("temperature").Attribute("value");

Answer 2

You could get json response and convert to dynamic obj using Newtonsoft.Json json converot or I believe any other convertor which could convert json to dynamic. This will help you to avoid parsing errors if scheme of returned object be changed.

using (WebClient wc = new Webclient())
{
    var json = wc.DownloadString("http://api.openweathermap.org/data/2.5/weather?q=London&mode=json");
    dynamic jsonResult = JsonConvert.DeserializeObject<ExpandoObject>(json , new ExpandoObjectConverter());

    // using dynamic object 
    var lon = jsonResult.coord.lon;
}