ここでは C# で JSON データを読む方法を紹介します。
DataContractJsonSerializer を使った方法です。
DataContractJsonSerializer.ReadObject() を使うと JSON データを読み、オブジェクトとして出力してくれます。
オブジェクトへの変換が「宣言」となっているところがいくらか分かりやすいといえるでしょうか。
まず、読み込みたいデータ構造をクラスとして宣言し、DataContract 属性を付加します。JSON データは DataMember 属性を付加します。ネストされているデータはクラスとして宣言しDataContract 属性を付加します。コードを参照してください。＃配列データは配列として宣言します。
出来上がったデータクラスを DataContractJsonSerializer のコンストラクタの引数として渡します。
準備が出来たらHttpWebResponse として読んできたデータを、DataContractJsonSerializer.ReadObject() で読み込みます。
と、この手順を踏むとめでたく JSON データが読み込めます。あとは出力するだけ。
ここの気温の表示はデフォルト設定でなんとＫ（ケルビン）です。ので 273.15 を引いてやります。
＃華氏（℉）か摂氏（℃）か迷ったんでしょうか（もめたんですかね）。
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| using System; | |
| using System.Collections.Generic; | |
| using System.IO; | |
| using System.Linq; | |
| using System.Runtime.Serialization; | |
| using System.Runtime.Serialization.Json; | |
| using System.Text; | |
| using System.Threading.Tasks; | |
| using System.Net; | |
| namespace JSONTest | |
| { | |
| class Program | |
| { | |
| static void Main(string[] args) | |
| { | |
| try | |
| { | |
| String url = "http://api.openweathermap.org/data/2.5/weather?q=chicago"; | |
| HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest; | |
| using (HttpWebResponse response = request.GetResponse() as HttpWebResponse) | |
| { | |
| if (response.StatusCode != HttpStatusCode.OK) | |
| throw new Exception(String.Format( | |
| "Server error (HTTP {0}: {1}).", | |
| response.StatusCode, | |
| response.StatusDescription)); | |
| DataContractJsonSerializer jsonSerializer = new DataContractJsonSerializer(typeof(Response)); | |
| object objResponse = jsonSerializer.ReadObject(response.GetResponseStream()); | |
| Response jsonResponse = objResponse as Response; | |
| //Console.WriteLine(jsonResponse.main.temp - 273.15); | |
| jsonSerializer.WriteObject(Console.OpenStandardOutput(), jsonResponse); | |
| Console.ReadLine(); | |
| } | |
| } | |
| catch (Exception e) | |
| { | |
| Console.Error.WriteLine(e.ToString()); | |
| //throw e; | |
| Console.ReadLine(); | |
| } | |
| } | |
| } | |
| [DataContract] | |
| public class Response | |
| { | |
| [DataMember(Name = "main")] | |
| public Main main { get; set; } | |
| [DataMember(Name = "coord")] | |
| public Coord coord { get; set; } | |
| [DataMember(Name = "sys")] | |
| public Sys sys { get; set; } | |
| [DataMember(Name = "weather")] | |
| public Weather[] weather { get; set; } | |
| [DataMember(Name = "wind")] | |
| public Wind wind { get; set; } | |
| [DataContract] | |
| public class Coord | |
| { | |
| [DataMember(Name = "lon")] | |
| public double lon { get; set; } | |
| [DataMember(Name = "lat")] | |
| public double lat { get; set; } | |
| } | |
| [DataContract] | |
| public class Sys | |
| { | |
| [DataMember(Name = "message")] | |
| public double message { get; set; } | |
| [DataMember(Name = "country")] | |
| public string country { get; set; } | |
| [DataMember(Name = "sunrise")] | |
| public long sunrise { get; set; } | |
| [DataMember(Name = "sunset")] | |
| public long sunset { get; set; } | |
| } | |
| [DataContract] | |
| public class Weather | |
| { | |
| [DataMember(Name = "id")] | |
| public long id { get; set; } | |
| [DataMember(Name = "main")] | |
| public string main { get; set; } | |
| [DataMember(Name = "description")] | |
| public string description { get; set; } | |
| [DataMember(Name = "icon")] | |
| public string icon { get; set; } | |
| } | |
| [DataMember(Name = "base")] | |
| public string _base { get; set; } | |
| [DataContract] | |
| public class Main | |
| { | |
| [DataMember(Name = "temp")] | |
| public double temp { get; set; } | |
| [DataMember(Name = "temp_min")] | |
| public double temp_min { get; set; } | |
| [DataMember(Name = "temp_max")] | |
| public double temp_max { get; set; } | |
| [DataMember(Name = "pressure")] | |
| public double pressure { get; set; } | |
| [DataMember(Name = "sea_level")] | |
| public double sea_level { get; set; } | |
| [DataMember(Name = "grnd_level")] | |
| public double grnd_level { get; set; } | |
| [DataMember(Name = "humidity")] | |
| public long humidity { get; set; } | |
| } | |
| [DataContract] | |
| public class Wind | |
| { | |
| [DataMember(Name = "speed")] | |
| public double speed { get; set; } | |
| [DataMember(Name = "deg")] | |
| public double deg { get; set; } | |
| } | |
| [DataContract] | |
| public class Clouds | |
| { | |
| [DataMember(Name = "all")] | |
| public long all { get; set; } | |
| } | |
| [DataMember(Name = "dt")] | |
| public long dt { get; set; } | |
| [DataMember(Name = "id")] | |
| public long id { get; set; } | |
| [DataMember(Name = "name")] | |
| public string name { get; set; } | |
| [DataMember(Name = "cod")] | |
| public long cod { get; set; } | |
| } | |
| } |
