使用System.Net.Http.HttpClient擴充去呼叫API
using System.Net.Http;
HttpClient Client = new HttpClient();
var response = Client.GetStringAsync(API URL).Result;
參考：
https://blog.kkbruce.net/2012/05/aspnet-web-api-8-http-http-message.html#.XQ-TTS8W5QI
https://blog.kkbruce.net/2012/05/aspnet-web-api-9-systemnethttphttpclien.html#.XQ-TTy8W5QI
