我们如何在 ASP.Net Core 中使用 HttpClient？

Question

我正在编写 ASP.Net MVC Core 2.2 Web 应用程序。我需要使用 HTTP 或 HTTPS 从另一个 Web 服务器获取数据。我该怎么做？

我使用HttpClient编写代码。

我有一个收到消息的控制器，它工作正常，但是我应该构造HttpClient吗？

[Route("api/[controller]")]
[ApiController]
public class MyController : ControllerBase
{
    private readonly IHostingEnvironment _env;
    private readonly ILogger _logger;
    private readonly IUpdateService _updateService;

    public MyController(
        IHostingEnvironment env,
        ILogger<MyController> logger,
        IUpdateService updateService)
    {
        _env = env;
        _logger = logger;
        _updateService = updateService;
    }

    // POST api/values
    [HttpPost]
    public async Task<IAsyncResult> Post([FromBody]Update update)
    {
        using (HttpClient Client = new HttpClient())
        {
            HttpResponseMessage result = Client.GetAsync(uri).Result;
            switch (result.StatusCode)
            {
                case HttpStatusCode.Accepted:
                    return true;
                case HttpStatusCode.OK:
                    return true;
                default:
                    return false;
            }
        }
    }
}

Answer 1

Microsoft documentation here.

1. 在ConfigureServices中注册HttpClient。

   1a。为typed clients

   services.AddHttpClient<ITypedClientService, TypedClientService>();
   

   1b。为named clients

   services.AddHttpClient("someClient", c =>
   {
       c.BaseAddress = new Uri("https://someaddress.com/");
   });
   

   1c。为Basic usage

   services.AddHttpClient();
   

2. 将HttpClient 注入您的控制器。

   [ApiController]
   public class BotController : ControllerBase
   {
       ...
   

   2a。为typed clients

       public BotController(..., ITypedClientService httpClient, ...)
       {
           ...
           _httpClient = httpClient;
           ...
       }
   

   2b。为named clients

       public BotController(..., IHttpClientFactory clientFactory, ...)
       {
           ...
           _httpClient = clientFactory.createClient("someClient");
           ...
       }
   

   2c。为Basic usage

       IHttpClientFactory _clientFactory
   
       public BotController(..., IHttpClientFactory clientFactory, ...)
       {
           ...
           _clientFactory = clientFactory; 
           ...
       }
   
       [HttpPost]
       public async Task<IActionResult> Post([FromBody]Update update)
       {
           ...
           var request = new HttpRequestMessage(
               HttpMethod.Get, 
               "https://someaddress.com/api/resource");
           request.Headers.Add("Accept", "application/vnd.github.v3+json");
           request.Headers.Add("User-Agent", "YourApp");
           var client = _clientFactory.createClient();
           var response = await client.SendAsync(request);
           ...
       }
   

不要自己构造HttpClient，新的就是胶水。让HttpClientFactory 和框架管理生命周期和实例化。

注意， 使用基本用法，您可以避开为定义的客户端配置策略的好处。