From the api call:

 var httpClient = new HttpClient();
 var uri = "https://api.postcodes.io/postcodes/";
 var response = await httpClient.PostAsync(uri, data);
 string result = response.Content.ReadAsStringAsync().Result;
 var list = JsonConvert.DeserializeObject<GeoDataList>(result);

with two custom classes:

  [Serializable]
    public class GeoData
{
    [JsonProperty("postcode")]
    public string postcode { get; set; }

    [JsonProperty("longitude")]
    public string longitude { get; set; }
    [JsonProperty("latitude")]
    public string latitude { get; set; }
}

    public class GeoDataList
    {
        [JsonProperty("result")]
        public List<GeoData> geoDatas { get; set; }
    }

The result contains this json-string:

{
  "status": 200,
  "result": [{
    "query": "OX49 5NU",
    "result": {
      "postcode": "OX49 5NU",
      "longitude": -1.069876,
      "latitude": 51.6562
    }
  }, {
    "query": "M32 0JG",
    "result": {
      "postcode": "M32 0JG",
      "longitude": -2.302836,
      "latitude": 53.455654
    }
  }, {
    "query": "NE30 1DP",
    "result": {
      "postcode": "NE30 1DP",
      "longitude": -1.439269,
      "latitude": 55.011303,
    }
  }]
}

The list contains 3 empty objects. postcode, longitude, and latitude are null. How do I populate the inner objects (GeoData)?

Kind regard /Rudy

CodePudding user response：

So, when we have to work with JSON and we really don't want to grunt all this out by hand, because it's tedious and liable to error, we go to http://quicktype.io (or json2csharp, or some similar site) and we paste our JSON in there..

We fix up any syntax errors in the json (quicktype shows a red bar in the json-paste window), like the trailing comma on the last result latitude, and we get this bunch of classes generated by QuickType:

// <auto-generated />
//
// To parse this JSON data, add NuGet 'Newtonsoft.Json' then do:
//
//    using SomeNamespace;
//
//    var root = Root.FromJson(jsonString);

namespace SomeNamespace
{
    using System;
    using System.Collections.Generic;

    using System.Globalization;
    using Newtonsoft.Json;
    using Newtonsoft.Json.Converters;

    public partial class Root
    {
        [JsonProperty("status")]
        public long Status { get; set; }

        [JsonProperty("result")]
        public ResultElement[] Result { get; set; }
    }

    public partial class ResultElement
    {
        [JsonProperty("query")]
        public string Query { get; set; }

        [JsonProperty("result")]
        public ResultResult Result { get; set; }
    }

    public partial class ResultResult
    {
        [JsonProperty("postcode")]
        public string Postcode { get; set; }

        [JsonProperty("longitude")]
        public double Longitude { get; set; }

        [JsonProperty("latitude")]
        public double Latitude { get; set; }
    }

    public partial class Root
    {
        public static Root FromJson(string json) => JsonConvert.DeserializeObject<Root>(json, SomeNamespace.Converter.Settings);
    }

    public static class Serialize
    {
        public static string ToJson(this Root self) => JsonConvert.SerializeObject(self, SomeNamespace.Converter.Settings);
    }

    internal static class Converter
    {
        public static readonly JsonSerializerSettings Settings = new JsonSerializerSettings
        {
            MetadataPropertyHandling = MetadataPropertyHandling.Ignore,
            DateParseHandling = DateParseHandling.None,
            Converters =
            {
                new IsoDateTimeConverter { DateTimeStyles = DateTimeStyles.AssumeUniversal }
            },
        };
    }
}

And the comment at the top tells us how to use it:

var root = Root.FromJson(jsonString);

And then if you just want the inner result objects you could:

root.Result.Select(r => r.Result).ToList()

If you don't like the class names that QT has picked, you can refactor/rename them in VS - the json will remain parsable because it also added all the [Jsonproeprty] attributes for you with the names as per the JSON so the C# props can be anything you like

QT is Newtonsoft oriented; if you want to use the generated classes with System.Text.Json you just have to adjust the attribute names with find/replace and a couple of other bits of tidy up

_{I have zero affiliation with QT}