C#でHTTP通信を行う

2019.03.23 2022.06.07

HttpClientクラスを使ってHTTP通信を行う方法です。

C#で HTTP POST を行う

PostAsync()メソッドを使用します。

下のコードはバイナリデータ(画像ファイル)と文字列をPOSTで送るサンプルです。

PostProcess.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Net.Http;

namespace PostTest {
    class PostProcess {
        private static PostProcess _single = null;

        private HttpClient _httpClient = null;


        private PostProcess() {
            _httpClient = new HttpClient();
        }

        ~PostProcess() {
            PostProcess.Dispose();
        }

        public static PostProcess GetInstance() {
            if (_single == null) {
                _single = new PostProcess();
            }
            return _single;
        }

        public static void Dispose() {
            if (_single == null) {
                return;
            }
            if (_single._httpClient == null) {
                return;
            }
            _single._httpClient.Dispose();
            _single = null;
        }

        public async void ExecuteHttpClient(Uri uri) {

            string imagePath = @"C:\Users\Default\Pictures\sample.jpg";

            MultipartFormDataContent content = new MultipartFormDataContent();
            // バイナリデータ.
            ByteArrayContent imageBytes = new ByteArrayContent(File.ReadAllBytes(imagePath));
            content.Add(imageBytes, "imagefile", Path.GetFileName(imagePath));

            // 文字列.
            content.Add(new StringContent("E195335D5206A8CC06312DC2717CB514"), "checkkey");
            content.Add(new StringContent("1"), "id");
            content.Add(new StringContent("sandy"), "name");

            var response = await _httpClient.PostAsync(uri, content);
            Debug.WriteLine(response.StatusCode == System.Net.HttpStatusCode.OK);
        }
    }
}

送信データはMultipartFormDataContentに詰めます。

呼び出し例

private void post() {
    PostProcess.GetInstance().ExecuteHttpClient(new Uri("http://localhost:8080/post-api"));
}

C#で HTTP GET を行う

GetAsync()メソッドを使用します。

GetProcess.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Net.Http;
using System.Web;

namespace GetTest {
    class GetProcess {
        private static GetProcess _single = null;

        private HttpClient _httpClient = null;

        private GetProcess() {
            _httpClient = new HttpClient();
        }

        ~GetProcess() {
            GetProcess.Dispose();
        }

        public static GetProcess GetInstance() {
            if (_single == null) {
                _single = new GetProcess();
            }
            return _single;
        }

        public static void Dispose() {
            if (_single == null) {
                return;
            }
            if (_single._httpClient == null) {
                _single = null;
                return;
            }
            _single._httpClient.Dispose();
            _single = null;
        }

        public async void ExecuteHttpClient(Uri uri, Dictionary<string, string> queries) {
            System.Collections.Specialized.NameValueCollection query = HttpUtility.ParseQueryString("");
            foreach (KeyValuePair<string, string> item in queries) {
                query.Add(item.Key, item.Value);
            }

            UriBuilder builder = new UriBuilder(uri.AbsoluteUri);
            builder.Query = query.ToString();

            var response = await _httpClient.GetAsync(builder.Uri);
            Debug.WriteLine(response.StatusCode == System.Net.HttpStatusCode.OK);
        }
    }
}

GETなので、パラメータはクエリ文字列で渡します。(実際のURLはbuilder.Uri.AbsoluteUriで確認できます)

呼び出し例

private void getTest() {
    Dictionary<string, string> queries = new Dictionary<string, string>();
    queries.Add("arg", "abcdefg");
    GetProcess.GetInstance().ExecuteHttpClient(new Uri("http://localhost:8080/get-api"), queries);
}