说明：一个用C#编写的WebAPI操作类，只写了Get Post 部分。

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

namespace Assets.Scripts.Models
{
    class WebAPIOperator
    {
        static string ip = ConfigMan.ReadNode("ServerSet", "ip");
        static string port = ConfigMan.ReadNode("ServerSet", "port");
        static string baseUri = "http://" + ip + ":" + port;
        /// <summary>
        /// 服务器通信状态
        /// </summary>
        public static bool NetState = true;

        public static HttpClient httpClient;

        #region CTOR
        private WebAPIOperator()
        {
            httpClient.BaseAddress = new Uri(baseUri);
            httpClient.DefaultRequestHeaders.Accept.Clear();
            httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("Application/json"));
        }
        #endregion

        #region Async Task
        public static async Task RunAsync()
        {
            httpClient.BaseAddress = new Uri(baseUri);
            httpClient.DefaultRequestHeaders.Accept.Clear();
            httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("Application/json"));

            try
            {
                //执行API任务
            }
            catch (Exception)
            {
                throw;
            }
        }
        #endregion

        #region init
        public static void initAPI()
        {
            ip = ConfigMan.ReadNode("ServerSet", "ip");
            port = ConfigMan.ReadNode("ServerSet", "port");
            baseUri = "http://" + ip + ":" + port;
            httpClient = new HttpClient();
            httpClient.BaseAddress = new Uri(baseUri);
            httpClient.DefaultRequestHeaders.Accept.Clear();
            httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("Application/json"));
            //系统默认超时100s
            //https://docs.microsoft.com/zh-cn/dotnet/api/system.net.http.httpclient.timeout?view=netframework-4.8#System_Net_Http_HttpClient_Timeout
            //httpClient.Timeout = TimeSpan.FromMinutes(1);//超时60s
        }
        #endregion

        #region Get
        /// <summary>
        /// WebAPI Get方法，返回JObject
        /// </summary>
        /// <param name="uri">带参数的uri</param>
        /// <returns></returns>
        public static async Task<JObject> GetAsync(string uri)
        {
            JObject o = null;
            try
            {
                HttpResponseMessage response = new HttpResponseMessage();
                response = await httpClient.GetAsync(uri);
                if (response != null && response.IsSuccessStatusCode)
                {
                    string jsonStr = await response.Content.ReadAsStringAsync();//获取JSON字符串
                    JObject jobj = JObject.Parse(jsonStr);//转换为JObject
                                                          //o=...
                                                          //保存数据到文件等
                                                          //List_Screen.Items.Add(jsonStr);
                    o = jobj;
                    NetState = true;
                }
                else
                {
                    NetState = false;
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                //更新网络状态
                NetState = false;
                //Log4NetHelper.Error("网络掉线", ex);
            }
            return o;
        }
        /// <summary>
        /// WebAPI GET方法，返回string json,用于反序列化
        /// </summary>
        /// <param name="uri"></param>
        /// <returns></returns>
        public static async Task<string> GetAsync_uri(string uri)
        {
            string jsonStr = "";
            try
            {
                HttpResponseMessage response = await httpClient.GetAsync(uri);
                if (response.IsSuccessStatusCode)
                {
                    jsonStr = await response.Content.ReadAsStringAsync();//获取JSON字符串
                                                                         //JObject jobj = JObject.Parse(jsonStr);//转换为JObject
                                                                         //o=...
                                                                         //保存数据到文件等
                                                                         //List_Screen.Items.Add(jsonStr);
                                                                         //o = jobj;
                }
                NetState = true;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                //更新网络状态
                NetState = false;
                //RoutedEventArgs args = new RoutedEventArgs(UpdateNetStateEvent);
                //new ImageButton().RaiseEvent(args);
                //Log4NetHelper.Error("网络掉线", ex);
            }

            return jsonStr;
        }
        #endregion

        #region POST
        public static async Task<string> PostAsync(string uri, Object obj)
        {
            string o = "";
            string jsonStr = JsonConvert.SerializeObject(obj);
            HttpResponseMessage response = await httpClient.PostAsJsonAsync<Object>(uri, obj);
            //response.EnsureSuccessStatusCode();//响应失败时，用于触发异常
            //return response.Headers.Location;
            if (response.IsSuccessStatusCode)
            {
                //string jsonStr = await response.Content.ReadAsStringAsync();//获取JSON字符串
                //JObject jobj = JObject.Parse(jsonStr);
                //o = jobj;
                //o = await response.Content.ReadAsAsync<object>();
                o = await response.Content.ReadAsStringAsync();
            }
            return o;
        }
        public static async Task<object> PostAsync(string uri, string userName, string password)
        {
            Object o = null;
            HttpContent httpContent = new StringContent("loginName=" + userName + "&password=" + password);
            httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/x-www-form-urlencoded");
            HttpResponseMessage response = await httpClient.PostAsync(uri, httpContent);
            if (response.IsSuccessStatusCode)
            {
                string jsonStr = await response.Content.ReadAsStringAsync();//获取JSON字符串
                JObject jobj = JObject.Parse(jsonStr);
                o = jobj;
            }
            return o;
        }
        #endregion

        #region PUT
        //static async Task<Object> PutAsync(string uri, Object o)
        //{
        //    HttpResponseMessage response = await httpClient.PutAsJsonAsync<Object>(uri + "//id=" + 123, o);
        //    response.EnsureSuccessStatusCode();
        //    o = await response.Content.ReadAsAsync<Object>();
        //    return o;
    }
    #endregion

    #region Delete
    //static async Task<HttpStatusCode> DeleteAsync(string uri, string id)
    //{
    //    HttpResponseMessage response = await httpClient.DeleteAsync(uri + "//" + id);
    //    return response.StatusCode;
    //}
    #endregion

}