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HttpClientFactory returns results of previous request

I have an ASP.NET Core Web API service built using .NET 6 that makes http requests using C# HttpClientFactory to external services.
The issue I am facing is that the second request with different arguments returns same result as for the previous request.
I tried clearing default headers at the start of every request no luck.
What worked for me:
RestSharp: https://restsharp.dev/
Using new HttpClient() instance instead of httpClientFactory.CreateClient()
I would like to make it work with httpClientFactory as this is the recommended way. Any thoughts why much appreciated.
// Each request has different access token but same body
public async Task<MyResponse> GetXyz(object requestBody, string accessToken)
{
var uri = "...";
return await this.httpClientFactory.CreateClient("GetXyz").PostAsync<MyResponse>(uri, requestBody, GetHeaders(accessToken));
}
private static IList<(string, string)> GetHeaders(string accessToken)
{
var headers = new List<(string, string)>
{
(HeaderNames.Accept, "application/json"),
};
if (!string.IsNullOrWhiteSpace(accessToken))
{
headers.Add((HeaderNames.Authorization, "Bearer " + accessToken));
}
return headers;
}
public static async Task<T> PostAsync<T>(this HttpClient httpClient, string uri, object data, IList<(string, string)> headers = null)
where T : class
{
// httpClient.DefaultRequestHeaders.Clear();
var body = data.Serialise(); // convert to JSON string
using (var request = new HttpRequestMessage(HttpMethod.Post, uri))
{
request.AddRequestHeaders(headers);
request.Content = new StringContent(body, Encoding.UTF8, "application/json");
using (var httpResponse = await httpClient.SendAsync(request))
{
var jsonResponse = await httpResponse.Content.ReadAsStringAsync();
return JsonSerializer.Deserialize<T>(jsonResponse);
}
}
}
EDIT 2: NETWORK TRAFFIC DIFF
Using Fiddler Classic with basic client httpclientfactory.CreateClient() here are the diffs between 2 requests headers that suffer from the issue:

Trouble posting more than once to webapi from Blazor component- "This instance has already started one or more requests." [duplicate]

I am creating an application in .Net Core 2.1 and I am using http client for web requests. The issue is I have to send parallel calls to save time and for that I am using Task.WhenAll() method but when I hit this method I get the error "This instance has already started one or more requests. Properties can only be modified before sending the first request" Previously I was using RestSharp and everything was fine but I want to use httpclient. Here is the code:
public async Task<User> AddUser(string email)
{
var url = "user/";
_client.BaseAddress = new Uri("https://myWeb.com/");
_client.DefaultRequestHeaders.Accept.Clear();
_client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(Constants."application/json"));
_client.DefaultRequestHeaders.Add("Authorization", "Bearer " + token);
var json = new {email = email }
var response = await _client.PostAsJsonAsync(url,json);
if (response .IsSuccessStatusCode)
{ ....
Here is the constructor:
private readonly HttpClient _httpClient;
public UserRepository(HttpClient httpClient)
{
_httpClient = httpClient;
}
Method calling:
var user1 = AddUser("user#user.com");
var user2 = AddUser("test#test.com");
await Task.WhenAll(user1, user2);
and here is the startup configuation:
services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
So what am I doing wrong? Do I need to change AddSingleton with AddTransient() or is there any other issue. One more question do I need to use _client.Dispose() after the response because the tutorial which I followed didn't use dispose method so I am little confused in that.

HttpClient.DefaultRequestHeaders (and BaseAddress) should only be set once, before you make any requests. HttpClient is only safe to use as a singleton if you don't modify it once it's in use.
Rather than setting DefaultRequestHeaders, set the headers on each HttpRequestMessage you are sending.
var request = new HttpRequestMessage(HttpMethod.Post, url);
request.Headers.Accept.Clear();
request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
request.Content = new StringContent("{...}", Encoding.UTF8, "application/json");
var response = await _client.SendAsync(request, CancellationToken.None);
Replace "{...}" with your JSON.

Maybe my two cents will help someone.
I ran into this issue when refreshing the page when debugging the application.
I was using a singleton, but each refresh, it was trying to set the base address. So I just wrapped it in a check to see if the base address had already been set.
The issue for me was, it was trying to set the baseAddress, even though it was already set. You can't do this with a httpClient.
if (_httpClient.BaseAddress == null)
{
_httpClient.BaseAddress = new Uri(baseAddress);
}

The issue is caused by resetting BaseAddress and headers for the same instance of the httpclient.
I tried
if (_httpClient.BaseAddress == null)
but I am not keen on this.
In my opinion, a better soloution is to use the httpclientFactory. This will terminate and garbage collect the instance of the httpclient after its use.
private readonly IHttpClientFactory _httpClientFactory;
public Foo (IHttpClientFactory httpClientFactory)
{
_httpClientFactory = httpClientFactory;
}
public httpresponse Bar ()
{
_httpClient = _httpClientFactory.CreateClient(command.ClientId);
using var response = await _httpclient.PostAsync(uri,content);
return response;
// here as there is no more reference to the _httpclient, the garbage collector will clean
// up the _httpclient and release that instance. Next time the method is called a new
// instance of the _httpclient is created
}

It Works well when you add the request url and the headers at the message, rather than at the client. So better not to assign to BaseAddress Or the header DefaultRequestHeaders if you will use them for many requests.
HttpRequestMessage msg = new HttpRequestMessage {
Method = HttpMethod.Put,
RequestUri = new Uri(url),
Headers = httpRequestHeaders;
};
httpClient.SendAsync(msg);

Why is ResponseMessage.Content consistently empty after an await PostAsJsonAsync request?

We are posting a "maintenanceEvent" to an API which consistently returns [] in ResponseMessage.Content. I'd need some expert guidance in case the code I wrote here is faulty.
private async Task SendMaintenanceEvent(object maintenanceEvent, MaintenanceEventType maintenanceEventType)
{
string endpointAddress = "TheEndpointURI";
string credentials = "OurCredentials";
string credentialsBase64 = Convert.ToBase64String(System.Text.ASCIIEncoding.ASCII.GetBytes(credentials));
// Convert the maintenanceEvent object to consumable JSON, then encode it to a StringContent object.
this.responseInfo.MaintenanceEventAsJSON = System.Web.Helpers.Json.Encode(maintenanceEvent);
StringContent stringContent = new StringContent(this.responseInfo.MaintenanceEventAsJSON, Encoding.UTF8, "application/json");
using (HttpClient httpClient = new HttpClient())
{
httpClient.BaseAddress = new Uri(endpointAddress);
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", credentialsBase64);
this.responseInfo.AuthorizationHeader = httpClient.DefaultRequestHeaders.Authorization.ToString();
this.responseInfo.EndpointUri = httpClient.BaseAddress.AbsoluteUri;
// The async post.
this.responseInfo.ResponseMessage = await httpClient.PostAsJsonAsync(access.EndpointDirectory, stringContent).ConfigureAwait(false);
this.responseInfo.ResponseStatusCode = (int)this.responseInfo.ResponseMessage.StatusCode;
// Consistently returns true so long as my credentials are valid.
// When the auth credentials are invalid, this returns false.
if (this.responseInfo.ResponseMessage.IsSuccessStatusCode)
{
// I expect to see some data from the service.
this.responseInfo.ResponseContent = this.responseInfo.ResponseMessage.Content.ReadAsStringAsync();
}
}
}
Try/Catch blocks and some company specific info is omitted. The responseInfo object above is just a model with some properties to collect information from this method, so we can record the event.
Where I suspect a problem may be, is in the code below the PostAsJsonAsync command. But I'm at a loss for what to do there. Thanks for your help.

This (slightly adjusted) is what you want to do (substitute your own variables as needed):
using (HttpClient httpClient = new HttpClient())
{
// ...
HttpResponseMessage responseMessage = await httpClient.PostAsJsonAsync(access.EndpointDirectory, stringContent).ConfigureAwait(false);
// ...
string responseBody = await responseMessage.Content.ReadAsStringAsync().ConfigureAwait(false);
// ...
}
I.e. you must await ReadAsStringAsync() to get the actual content.
For completeness, note that HttpResponseMessage and HttpResponseMessage.Content are IDisposable.

How can I add a HTTP Header called "Content-Type" to an HttpClient request? [duplicate]

I need to add http headers to the HttpClient before I send a request to a web service. How do I do that for an individual request (as opposed to on the HttpClient to all future requests)? I'm not sure if this is even possible.
var client = new HttpClient();
var task =
client.GetAsync("http://www.someURI.com")
.ContinueWith((taskwithmsg) =>
{
var response = taskwithmsg.Result;
var jsonTask = response.Content.ReadAsAsync<JsonObject>();
jsonTask.Wait();
var jsonObject = jsonTask.Result;
});
task.Wait();

Create a HttpRequestMessage, set the Method to GET, set your headers and then use SendAsync instead of GetAsync.
var client = new HttpClient();
var request = new HttpRequestMessage() {
RequestUri = new Uri("http://www.someURI.com"),
Method = HttpMethod.Get,
};
request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("text/plain"));
var task = client.SendAsync(request)
.ContinueWith((taskwithmsg) =>
{
var response = taskwithmsg.Result;
var jsonTask = response.Content.ReadAsAsync<JsonObject>();
jsonTask.Wait();
var jsonObject = jsonTask.Result;
});
task.Wait();

When it can be the same header for all requests or you dispose the client after each request you can use the DefaultRequestHeaders.Add option:
client.DefaultRequestHeaders.Add("apikey","xxxxxxxxx");

To set custom headers ON A REQUEST, build a request with the custom header before passing it to httpclient to send to http server.
eg:
HttpClient client = HttpClients.custom().build();
HttpUriRequest request = RequestBuilder.get()
.setUri(someURL)
.setHeader(HttpHeaders.CONTENT_TYPE, "application/json")
.build();
client.execute(request);
Default header is SET ON HTTPCLIENT to send on every request to the server.

.NET HttpClient Request Content-Type

I'm not sure, but it appears to me that the default implementation of .NET HttpClient library is flawed. It looks like it sets the Content-Type request value to "text/html" on a PostAsJsonAsync call. I've tried to reset the request value, but not sure if I'm doing this correctly. Any suggestions.
public async Task<string> SendPost(Model model)
{
var client = new HttpClient();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
var response = await client.PostAsJsonAsync(Url + "api/foo/", model);
response.EnsureSuccessStatusCode();
return await response.Content.ReadAsStringAsync();
}

You should set the content type. With the Accept you define what you want as response.
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
The Accept request-header field can be used to specify certain media types which are acceptable for the response. Accept headers can be used to indicate that the request is specifically limited to a small set of desired types, as in the case of a request for an in-line image.
public async Task<string> SendPost(Model model)
{
var client = new HttpClient(); //You should extract this and reuse the same instance multiple times.
var request = new HttpRequestMessage(HttpMethod.Post, Url + "api/foo");
using(var content = new StringContent(Serialize(model), Encoding.UTF8, "application/json"))
{
request.Content = content;
var response = await client.SendAsync(request).ConfigureAwait(false);
response.EnsureSuccessStatusCode();
return await response.Content.ReadAsStringAsync().ConfigureAwait(false);
}
}