Adding headers when using httpClient.GetAsync

I'm implementing an API made by other colleagues with Apiary.io, in a Windows Store app project.

They show this example of a method I have to implement:

var baseAddress = new Uri("https://private-a8014-xxxxxx.apiary-mock.com/");

using (var httpClient = new HttpClient{ BaseAddress = baseAddress })
{
    using (var response = await httpClient.GetAsync("user/list{?organizationId}"))
    {
        string responseData = await response.Content.ReadAsStringAsync();
    }
}

In this and some other methods, I need to have a header with a token that I get before.

Here's an image of Postman (chrome extension) with the header I'm talking about:

How do I add that Authorization header to the request?

A later answer, but because no one gave this solution...

If you do not want to set the header on the HttpClient instance by adding it to the DefaultRequestHeaders, you could set headers per request.

But you will be obliged to use the SendAsync() method.

This is the right solution if you want to reuse the HttpClient -- which is a good practice for

• performance and port exhaustion problems
• doing something thread-safe
• not sending the same headers every time

Use it like this:

using (var requestMessage =
            new HttpRequestMessage(HttpMethod.Get, "https://your.site.com"))
{
    requestMessage.Headers.Authorization =
        new AuthenticationHeaderValue("Bearer", your_token);
    
    await httpClient.SendAsync(requestMessage);
}

When using GetAsync with the HttpClient you can add the authorization headers like so:

httpClient.DefaultRequestHeaders.Authorization 
                         = new AuthenticationHeaderValue("Bearer", "Your Oauth token");

This does add the authorization header for the lifetime of the HttpClient so is useful if you are hitting one site where the authorization header doesn't change.

Here is an detailed SO answer

The accepted answer works but can got complicated when I wanted to try adding Accept headers. This is what I ended up with. It seems simpler to me so I think I'll stick with it in the future:

client.DefaultRequestHeaders.Add("Accept", "application/*+xml;version=5.1");
client.DefaultRequestHeaders.Add("Authorization", "Basic " + authstring);

Sometimes, you only need this code.

 httpClient.DefaultRequestHeaders.Add("token", token);

Following the greenhoorn's answer, you can use "Extensions" like this:

  public static class HttpClientExtensions
    {
        public static HttpClient AddTokenToHeader(this HttpClient cl, string token)
        {
            //int timeoutSec = 90;
            //cl.Timeout = new TimeSpan(0, 0, timeoutSec);
            string contentType = "application/json";
            cl.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(contentType));
            cl.DefaultRequestHeaders.Add("Authorization", String.Format("Bearer {0}", token));
            var userAgent = "d-fens HttpClient";
            cl.DefaultRequestHeaders.Add("User-Agent", userAgent);
            return cl;
        }
    }

And use:

string _tokenUpdated = "TOKEN";
HttpClient _client;
_client.AddTokenToHeader(_tokenUpdated).GetAsync("/api/values")

You can add whatever headers you need to the HttpClient.

Here is a nice tutorial about it.

This doesn't just reference to POST-requests, you can also use it for GET-requests.

These days, if you are using MS Dependency Injection, it's highly recomended to plug in the IHttpClientFactory:

builder.Services.AddHttpClient("GitHub", httpClient =>
{
    httpClient.BaseAddress = new Uri("https://api.github.com/");

    // using Microsoft.Net.Http.Headers;
    // The GitHub API requires two headers.
    httpClient.DefaultRequestHeaders.Add(
        HeaderNames.Accept, "application/vnd.github.v3+json");
    httpClient.DefaultRequestHeaders.Add(
        HeaderNames.UserAgent, "HttpRequestsSample");
});

var httpClient = _httpClientFactory.CreateClient("GitHub");

This way you avoid adding default request headers to a globally shared httpclient and moreover don't have to deal with manual creation of the HttpRequestMessage.

Source: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-6.0#consumption-patterns