How to access my json data from API using c# xamarin

Question

I try to receive my data from my API point, but everytime I receive message:

    result  Id = 1, Status = WaitingForActivation, Method = {null}

This is my ResService_HQ_AHS class:

using System;
using System.Diagnostics;
using System.Net.Http;
using System.Threading.Tasks;
using HydroMeteoAnalyzer.Models.API;
using Newtonsoft.Json;

namespace HydroMeteoAnalyzer.Services
{
    public class RestService_HQ_AHS
    {
        HttpClient _client;

        public RestService_HQ_AHS()
        {
            _client = new HttpClient();
        }

        public async Task<HQ_AHS> Get_HQ_AHS(string query)
        {
            HQ_AHS HQ_Data = new HQ_AHS();

            try
            {
                var response = await _client.GetAsync(query);
                if (response.IsSuccessStatusCode)
                {
                    var content = await response.Content.ReadAsStringAsync();
                    HQ_Data = JsonConvert.DeserializeObject<HQ_AHS>(content);
                }
            }
            catch (Exception ex)
            {
                Debug.WriteLine("\t\tERROR {0}", ex.Message);
            }

            return HQ_Data;
        }
    }
}

Here is the object from json:

using System;
namespace HydroMeteoAnalyzer.Models.API
{
    public class HQ_AHS
    {
        public int Station { get; set; }
        public string Ime { get; set; }
    }
}

Here is my Constants class with API EndPoint:

using System;
namespace HydroMeteoAnalyzer.Models.API
{
    public class Constants
    {
        public static string EndPoint = "http://194.141.118.43/api/stations";
    }
}

Here is my page which I try to receive the data from Json file:

    using System;
using System.Collections.Generic;
using HydroMeteoAnalyzer.Models.API;
using HydroMeteoAnalyzer.Services;
using Xamarin.Forms;

namespace HydroMeteoAnalyzer.Models.Hydro
{   
    public partial class HQ_AHS : ContentPage
    {
        RestService_HQ_AHS  _restServiceStations;
        public HQ_AHS ()
        {
            InitializeComponent ();
            _restServiceStations = new RestService_HQ_AHS();
            CheckStation_HQ_AHS();
        }

        string GenerateRequestUriStations(string endpoint)
        {
            string requestUri = endpoint;
            requestUri += $"stations";

            return requestUri;
        }

        public void CheckStation_HQ_AHS()
        {
            var result = _restServiceStations.Get_HQ_AHS(Constants.EndPoint);

            var test = result;
        }
    }
}

Everytime I receive null on my test and receive message:result Id = 1, Status = WaitingForActivation, Method = {null} and In the RestService_HQ_AHS cannot enter in the If statement..

This is the API point: http://194.141.118.43/api/stations

What do I need to change to get my data from the API ?

haldo · Accepted Answer · 2022-02-13 13:28:54Z

1

The problem is that you're not awaiting the response from Get_HQ_AHS. This needs to be awaited in the CheckStation_HQ_AHS method. Update the signature to async Task too (async void should generally be avoided):

public async Task CheckStation_HQ_AHS()
{
    var result = await _restServiceStations.Get_HQ_AHS(Constants.EndPoint);
    ...
}

Additionally, the json response is a list/array of type List<HQ_AHS>, so you should try deserializing using:

var content = await response.Content.ReadAsStringAsync();
var responseModel = JsonConvert.DeserializeObject<List<HQ_AHS>>(content);
//                       deserialize to list here ^^^

You haven't shown HQ_Data so not sure how the response maps to that class, but you should be able to deserialize using the above code.

edited Feb 13, 2022 at 13:28

answered Feb 13, 2022 at 12:45

haldo

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6 Comments

Ben Johnson Over a year ago

Yes, now as a result I see that the objects are coming but "Station" property come 0 "Ime" property come null. Another thing I notice is that in the file RestService_HQ_AHS Unable to enter the if statement..

haldo Over a year ago

@BenJohnson That explains why you're getting default values in the response - if it's not going in the if statement then the request doesn't have a 200 success code so something went wrong. Try to debug the issue. What is the actual response code? 400 bad request, 500 server error...?

Ben Johnson Over a year ago

ex {Java.IO.IOException: Cleartext HTTP traffic to 194.141.118.43 not permitted at Java.Interop.JniEnvironment+InstanceMethods.CallVoidMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x00…}

haldo Over a year ago

That's an error coming from Android/Java. I'm not sure if this will resolve the issue but you can try adding this to the Android manifest: android:usesCleartextTraffic="true". See this post for more options. Maybe try using https instead? @BenJohnson

Ben Johnson Over a year ago

With this code android:usesCleartextTraffic="true" I see the data in response in RestService_HQ_AHS, but I can't see data in var result = await _restServiceStations.Get_HQ_AHS(Constants.EndPoint); I still see the "Station" property is 0 and "Ime" property is null..

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