How can we use HttpClient in ASP.Net Core?

Question

I'm writing ASP.Net MVC Core 2.2 Web App. I need to get data from another web server with HTTP or HTTPS. How should I do this?

I wrote code using HttpClient.

I have a Controller that gets a message and it works fine but, should I be constructing HttpClient?

[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;
            }
        }
    }
}

please, don't use using because of the IDispose pattern.. stackoverflow.com/a/54707165/1498669 — Bernhard
– Bernhard, Commented Mar 28, 2023 at 8:05

Jodrell · Accepted Answer · 2019-04-25 15:19:15Z

57

Microsoft documentation here.

Register the HttpClient in ConfigureServices.

1a. for typed clients

services.AddHttpClient<ITypedClientService, TypedClientService>();

1b. for named clients

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

1c. for Basic usage

services.AddHttpClient();

Inject the HttpClient into your controller.

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

2a. for typed clients

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

2b. for named clients

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

2c. for 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);
        ...
    }

Do not construct HttpClient yourself, new is glue. Let HttpClientFactory and the framework mangage the lifetimes and instantiation.

Note, With Basic Usage you are dodging the benefits of configuring policies for defined clients.

edited Apr 25, 2019 at 15:19

answered Apr 25, 2019 at 13:19

Jodrell

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5 Comments

poke Over a year ago

Better use HttpClientFactory instead.

Jodrell Over a year ago

@poke, that is essentially what I mean

Faraz Over a year ago

but I have question how can I send url to service in this way because every time the requested url is deferent?

Jodrell Over a year ago

@Faraz that is Basic usage

Jodrell Over a year ago

@Faraz, I extended the answer

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