HttpClient Usage

The correct usage of the HttpClient class.

Calling / using the HttpClient class in the following manner may seem like the obvious way to use it.

using (var client = new HttpClient())
{
  // use the client object
}

However, this could result in a “Circuit Exhaustion” error when volume or load is increased.

The following is the correct, recommended usage.

• Add a reference to the “Microsoft.Extensions.Http” package, which includes the IHttpClientFactory interface.
• In the main method, use dependency inject to obtain an instance of the “IHttpClientFactory” interface.

static async Task Main(string[] args)
{
    var serviceProvider = new ServiceCollection()
        .AddHttpClient()
        .BuildServiceProvider();

    // Save this to a variable that can be retrieved / used later.
    var httpClientFactory = serviceProvider.GetService<IHttpClientFactory>();
}

• To create an HTTP client using the factory, you can use the CreateClient method and specify a name for the client:

var client = httpClientFactory.CreateClient("myClient");

• Use the client to send an HTTP request and receive a response:

var response = await client.GetAsync("https://www.example.com");

if (response.IsSuccessStatusCode)
{
    var content = await response.Content.ReadAsStringAsync();
    Console.WriteLine(content);
}

• Dispose of the client when you're finished with it:

client.Dispose();

• Alternatively, you can use a using block to automatically dispose of the client when it goes out of scope:

using (var client = httpClientFactory.CreateClient("myClient"))
{
    var response = await client.GetAsync("https://www.example.com");

    if (response.IsSuccessStatusCode)
    {
        var content = await response.Content.ReadAsStringAsync();
        Console.WriteLine(content);
    }
}