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 App。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.

我有一个接收消息的控制器，它工作正常，但是，我应该构建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

微软文档在这里。

1. 注册HttpClient在ConfigureServices。

   1a. 对于打字客户

   services.AddHttpClient<ITypedClientService, TypedClientService>();
   

   1b. 对于指定客户

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

   1c。对于基本用法

   services.AddHttpClient();
   

2. 将 注入HttpClient到您的控制器中。

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

   2a. 对于打字客户

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

   2b. 对于指定客户

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

   2c。对于基本用法

       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HttpClient自己建造，新的就是胶水。让HttpClientFactory和框架管理生命周期和实例化。

请注意，使用基本用法，您将避免为定义的客户端配置策略的好处。