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Trying to pass several headers in get request [duplicate]

I'm trying to set the Content-Type header of an HttpClient object as required by an API I am calling.
I tried setting the Content-Type like below:
using (var httpClient = new HttpClient())
{
httpClient.BaseAddress = new Uri("http://example.com/");
httpClient.DefaultRequestHeaders.Add("Accept", "application/json");
httpClient.DefaultRequestHeaders.Add("Content-Type", "application/json");
// ...
}
It allows me to add the Accept header but when I try to add Content-Type it throws the following exception:
Misused header name. Make sure request headers are used with
HttpRequestMessage, response headers with HttpResponseMessage, and
content headers with HttpContent objects.
How can I set the Content-Type header in a HttpClient request?

The content type is a header of the content, not of the request, which is why this is failing. AddWithoutValidation as suggested by Robert Levy may work, but you can also set the content type when creating the request content itself (note that the code snippet adds application/json in two places-for Accept and Content-Type headers):
HttpClient client = new HttpClient();
client.BaseAddress = new Uri("http://example.com/");
client.DefaultRequestHeaders
.Accept
.Add(new MediaTypeWithQualityHeaderValue("application/json"));//ACCEPT header
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, "relativeAddress");
request.Content = new StringContent("{\"name\":\"John Doe\",\"age\":33}",
Encoding.UTF8,
"application/json");//CONTENT-TYPE header
client.SendAsync(request)
.ContinueWith(responseTask =>
{
Console.WriteLine("Response: {0}", responseTask.Result);
});

For those who didn't see Johns comment to carlos solution ...
req.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

If you don't mind a small library dependency, Flurl.Http [disclosure: I'm the author] makes this uber-simple. Its PostJsonAsync method takes care of both serializing the content and setting the content-type header, and ReceiveJson deserializes the response. If the accept header is required you'll need to set that yourself, but Flurl provides a pretty clean way to do that too:
using Flurl.Http;
var result = await "http://example.com/"
.WithHeader("Accept", "application/json")
.PostJsonAsync(new { ... })
.ReceiveJson<TResult>();
Flurl uses HttpClient and Json.NET under the hood, and it's a PCL so it'll work on a variety of platforms.
PM> Install-Package Flurl.Http

try to use TryAddWithoutValidation
var client = new HttpClient();
client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/json; charset=utf-8");

.Net tries to force you to obey certain standards, namely that the Content-Type header can only be specified on requests that have content (e.g. POST, PUT, etc.). Therefore, as others have indicated, the preferred way to set the Content-Type header is through the HttpContent.Headers.ContentType property.
With that said, certain APIs (such as the LiquidFiles Api, as of 2016-12-19) requires setting the Content-Type header for a GET request. .Net will not allow setting this header on the request itself -- even using TryAddWithoutValidation. Furthermore, you cannot specify a Content for the request -- even if it is of zero-length. The only way I could seem to get around this was to resort to reflection. The code (in case some else needs it) is
var field = typeof(System.Net.Http.Headers.HttpRequestHeaders)
.GetField("invalidHeaders", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static)
?? typeof(System.Net.Http.Headers.HttpRequestHeaders)
.GetField("s_invalidHeaders", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
if (field != null)
{
var invalidFields = (HashSet<string>)field.GetValue(null);
invalidFields.Remove("Content-Type");
}
_client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "text/xml");
Edit:
As noted in the comments, this field has different names in different versions of the dll. In the source code on GitHub, the field is currently named s_invalidHeaders. The example has been modified to account for this per the suggestion of #David Thompson.

For those who troubled with charset
I had very special case that the service provider didn't accept charset, and they refuse to change the substructure to allow it...
Unfortunately HttpClient was setting the header automatically through StringContent, and no matter if you pass null or Encoding.UTF8, it will always set the charset...
Today i was on the edge to change the sub-system; moving from HttpClient to anything else, that something came to my mind..., why not use reflection to empty out the "charset"? ...
And before i even try it, i thought of a way, "maybe I can change it after initialization", and that worked.
Here's how you can set the exact "application/json" header without "; charset=utf-8".
var jsonRequest = JsonSerializeObject(req, options); // Custom function that parse object to string
var stringContent = new StringContent(jsonRequest, Encoding.UTF8, "application/json");
stringContent.Headers.ContentType.CharSet = null;
return stringContent;
Note: The null value in following won't work, and append "; charset=utf-8"
return new StringContent(jsonRequest, null, "application/json");
EDIT
#DesertFoxAZ suggests that also the following code can be used and works fine. (didn't test it myself, if it work's rate and credit him in comments)
stringContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");

Some extra information about .NET Core (after reading erdomke's post about setting a private field to supply the content-type on a request that doesn't have content)...
After debugging my code, I can't see the private field to set via reflection - so I thought I'd try to recreate the problem.
I have tried the following code using .Net 4.6:
HttpRequestMessage httpRequest = new HttpRequestMessage(HttpMethod.Get, #"myUrl");
httpRequest.Content = new StringContent(string.Empty, Encoding.UTF8, "application/json");
HttpClient client = new HttpClient();
Task<HttpResponseMessage> response = client.SendAsync(httpRequest); //I know I should have used async/await here!
var result = response.Result;
And, as expected, I get an aggregate exception with the content "Cannot send a content-body with this verb-type."
However, if i do the same thing with .NET Core (1.1) - I don't get an exception. My request was quite happily answered by my server application, and the content-type was picked up.
I was pleasantly surprised about that, and I hope it helps someone!

Call AddWithoutValidation instead of Add (see this MSDN link).
Alternatively, I'm guessing the API you are using really only requires this for POST or PUT requests (not ordinary GET requests). In that case, when you call HttpClient.PostAsync and pass in an HttpContent, set this on the Headers property of that HttpContent object.

The trick is that you can just set all kinds of headers like:
HttpRequestMessage request = new HttpRequestMessage();
request.Headers.Add("Accept-Language", "en"); //works OK
but not any header. For example:
request.Headers.Add("Content-Type", "application/json");//wrong
will raise the run-time exception Misused header name. It may seem that this will work:
request.Headers.Add(
HttpRequestHeader.ContentType.ToString(), //useless
"application/json"
);
but this gives a useless header named ContentType, without the hyphen. Header names are not case-sensitive, but are very hyphen-sensitive.
The solution is to declare the encoding and type of the body when adding the body to the Content part of the http request:
string Body = "...";
request.Content =
new StringContent(Body, Encoding.UTF8, "application/json");
Only then the applicable http header is automatically added to the request:
Content-Type: application/json; charset=utf-8
It was hard to find this out, with Fiddler, on a machine without a proxy server. Visual Studio used to have a Network Tool where you could inspect all headers, but only in version 2015, not in newer versions 2017 or 2022. If you use the debugger to inspect request.Headers, you will not find the header added automagically by StringContent().

var content = new JsonContent();
content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
content.Headers.ContentType.Parameters.Add(new NameValueHeaderValue("charset", "utf-8"));
content.Headers.ContentType.Parameters.Add(new NameValueHeaderValue("IEEE754Compatible", "true"));
It's all what you need.
With using Newtonsoft.Json, if you need a content as json string.
public class JsonContent : HttpContent
{
private readonly MemoryStream _stream = new MemoryStream();
~JsonContent()
{
_stream.Dispose();
}
public JsonContent(object value)
{
Headers.ContentType = new MediaTypeHeaderValue("application/json");
using (var contexStream = new MemoryStream())
using (var jw = new JsonTextWriter(new StreamWriter(contexStream)) { Formatting = Formatting.Indented })
{
var serializer = new JsonSerializer();
serializer.Serialize(jw, value);
jw.Flush();
contexStream.Position = 0;
contexStream.WriteTo(_stream);
}
_stream.Position = 0;
}
private JsonContent(string content)
{
Headers.ContentType = new MediaTypeHeaderValue("application/json");
using (var contexStream = new MemoryStream())
using (var sw = new StreamWriter(contexStream))
{
sw.Write(content);
sw.Flush();
contexStream.Position = 0;
contexStream.WriteTo(_stream);
}
_stream.Position = 0;
}
protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
{
return _stream.CopyToAsync(stream);
}
protected override bool TryComputeLength(out long length)
{
length = _stream.Length;
return true;
}
public static HttpContent FromFile(string filepath)
{
var content = File.ReadAllText(filepath);
return new JsonContent(content);
}
public string ToJsonString()
{
return Encoding.ASCII.GetString(_stream.GetBuffer(), 0, _stream.GetBuffer().Length).Trim();
}
}

It appears that Microsoft tries to force the developers to follow their standards, without even giving any options or settings to do otherwise, which is really a shame especially given that this is a client and we are dictated by the server side requirements, especially given that Microsoft server side frameworks themselves require it!
So basically Microsoft tries to force us good habits when connecting to their server technologies that force us non good habits...
If anyone from Microsoft is reading this, then please fix it...
Either way for anyone that needs the content-type header for Get etc., while in an older .Net version it is possible to use the answer of #erdomke at https://stackoverflow.com/a/41231353/640195 this unfortunately no longer works in the newer .Net core versions.
The following code has been tested to work with .Net core 3.1 and from the source code on GitHub it looks like it should work with newer .Net versions as well.
private void FixContentTypeHeaders()
{
var assembly = typeof(System.Net.Http.Headers.HttpRequestHeaders).Assembly;
var assemblyTypes = assembly.GetTypes();
var knownHeaderType = assemblyTypes.FirstOrDefault(n => n.Name == "KnownHeader");
var headerTypeField = knownHeaderType?
.GetFields(System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)
.FirstOrDefault(n => n.Name.Contains("HeaderType"));
if (headerTypeField is null) return;
var headerTypeFieldType = headerTypeField.FieldType;
var newValue = Enum.Parse(headerTypeFieldType, "All");
var knownHeadersType = assemblyTypes.FirstOrDefault(n => n.Name == "KnownHeaders");
var contentTypeObj = knownHeadersType.GetFields().FirstOrDefault(n => n.Name == "ContentType").GetValue(null);
if (contentTypeObj is null) return;
headerTypeField.SetValue(contentTypeObj, newValue);
}

You can use this it will be work!
HttpRequestMessage msg = new HttpRequestMessage(HttpMethod.Get,"URL");
msg.Content = new StringContent(string.Empty, Encoding.UTF8, "application/json");
HttpResponseMessage response = await _httpClient.SendAsync(msg);
response.EnsureSuccessStatusCode();
string json = await response.Content.ReadAsStringAsync();

Ok, it's not HTTPClient but if u can use it, WebClient is quite easy:
using (var client = new System.Net.WebClient())
{
client.Headers.Add("Accept", "application/json");
client.Headers.Add("Content-Type", "application/json; charset=utf-8");
client.DownloadString(...);
}

try to use HttpClientFactory
services.AddSingleton<WebRequestXXX>()
.AddHttpClient<WebRequestXXX>("ClientX", config =>
{
config.BaseAddress = new System.Uri("https://jsonplaceholder.typicode.com");
config.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
config.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/json; charset=utf-8");
});
======================
public class WebRequestXXXX
{
private readonly IHttpClientFactory _httpClientFactory;
public WebRequestXXXX(IHttpClientFactory httpClientFactory)
{
_httpClientFactory = httpClientFactory;
}
public List<Posts> GetAllPosts()
{
using (var _client = _httpClientFactory.CreateClient("ClientX"))
{
var response = _client.GetAsync("/posts").Result;
if (response.IsSuccessStatusCode)
{
var itemString = response.Content.ReadAsStringAsync().Result;
var itemJson = System.Text.Json.JsonSerializer.Deserialize<List<Posts>>(itemString,
new System.Text.Json.JsonSerializerOptions
{
PropertyNameCaseInsensitive = true
});
return itemJson;
}
else
{
return new List<Posts>();
}
}
}
}

I got the answer whith RestSharp:
private async Task<string> GetAccessTokenAsync()
{
var client = new RestClient(_baseURL);
var request = new RestRequest("auth/v1/login", Method.POST, DataFormat.Json);
request.AddHeader("Content-Type", "application/json");
request.AddHeader("x-api-key", _apiKey);
request.AddHeader("Accept-Language", "br");
request.AddHeader("x-client-tenant", "1");
...
}
It worked for me.

You need to do it like this:
HttpContent httpContent = new StringContent(#"{ the json string }");
httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
HttpResponseMessage message = client.PostAsync(#"{url}", httpContent).Result;

For those wanting to set the Content-Type to Json specifically, you can use the extension method PostAsJsonAsync.
using System.Net.Http.Json; //this is needed for PostAsJsonAsync to work
//....
HttpClient client = new HttpClient();
HttpResponseMessage response = await
client.PostAsJsonAsync("http://example.com/" + "relativeAddress",
new
{
name = "John Doe",
age = 33
});
//Do what you need to do with your response
The advantage here is cleaner code and you get to avoid stringified json. More details can be found at: https://learn.microsoft.com/en-us/previous-versions/aspnet/hh944339(v=vs.118)

I find it most simple and easy to understand in the following way:
async Task SendPostRequest()
{
HttpClient client = new HttpClient();
var requestContent = new StringContent(<content>);
requestContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
var response = await client.PostAsync(<url>, requestContent);
var responseString = await response.Content.ReadAsStringAsync();
}
...
SendPostRequest().Wait();

I end up having similar issue.
So I discovered that the Software PostMan can generate code when clicking the "Code" button at upper/left corner. From that we can see what going on "under the hood" and the HTTP call is generated in many code language; curl command, C# RestShart, java, nodeJs, ...
That helped me a lot and instead of using .Net base HttpClient I ended up using RestSharp nuget package.
Hope that can help someone else!

Api returned
"Unsupported Media Type","status":415
Adding ContentType to the jsonstring did the magic and this is my script working 100% as of today
using (var client = new HttpClient())
{
var endpoint = "api/endpoint;
var userName = "xxxxxxxxxx";
var passwd = "xxxxxxxxxx";
var content = new StringContent(jsonString, Encoding.UTF8, "application/json");
var authToken = Encoding.ASCII.GetBytes($"{userName}:{passwd}");
client.BaseAddress = new Uri("https://example.com/");
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(authToken));
HttpResponseMessage response = await client.PostAsync(endpoint, content);
if (response.IsSuccessStatusCode)
{
// Get the URI of the created resource.
Uri returnUrl = response.Headers.Location;
Console.WriteLine(returnUrl);
}
string responseBody = await response.Content.ReadAsStringAsync();
return responseBody;
}

For my scenario, a third-party API was creating the HttpRequestMessage, so I was not able to use the top-voted answers to resolve the issue. And I didn't like the idea of messing with reflection so the other answers didn't work either.
Instead, I extended from AndroidMessageHandler and used this new class as a parameter to HttpClient. AndroidMessageHandler contains the method SendAsync which can be overridden in order to make changes to the HttpRequestMessage object before it is sent. If you don't have access to the Android Xamarin libaries, you may be able to figure something out with HttpMessageHandler.
public class XamarinHttpMessageHandler : global::Xamarin.Android.Net.AndroidMessageHandler
{
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
// Here I make check that I'm only modifying a specific request
// and not all of them.
if (request.RequestUri != null && request.RequestUri.AbsolutePath.EndsWith("download") && request.Content != null)
{
request.Content.Headers.Add("Content-Type", "text/plain");
}
return base.SendAsync(request, cancellationToken);
}
}
Then to use:
var client = new HttpClient(new XamarinHttpMessageHandler());

So if you're trying to do a /$batch OData request like this Microsoft article demonstrates where you're supposed to have a Content-Type header like:
Content-Type: multipart/mixed;boundary=batch_d3bcb804-ee77-4921-9a45-761f98d32029
string headerValue = "multipart/mixed;boundary=batch_d3bcb804-ee77-4921-9a45-761f98d32029";
//You need to set it like thus:
request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse(headerValue);
Again, the magic you need is: MediaTypeHeaderValue.Parse(...)

stringContent.Headers.ContentType = new MediaTypeHeaderValue(contentType);
And 🎉 YES! 🎉 ... that cleared up the problem with ATS REST API: SharedKey works now! 😄 👍 🍻
Source: https://github.com/dotnet/runtime/issues/17036#issuecomment-212046628

C# HttpRequestMessage Content-Type force as "application/json" only [duplicate]

This question already has answers here:
How to remove the default charset in HttpClient Request Header C#
(2 answers)
Closed 1 year ago.
I'm creating an HttpClient request to post an object to an API endpoint. The API endpoint only accepts "application/json" but my application changes the type to "application/json; charset=utf-8" which the API won't accept. What do I change in the StringContent to make it so it is only 'application/json'? I tried changing the encoding type from Default to null to UTF8 but that has not changed it.
var httpClientHandler = new HttpClientHandler();
httpClientHandler.ServerCertificateCustomValidationCallback = (message, cert, chain, sslPolicyErrors) =>
{
true;
};
var client = new HttpClient(httpClientHandler);
var webRequest = new HttpRequestMessage(HttpMethod.Post, base_url + url)
{
Content = new StringContent(body, Encoding.Default, "application/json")
};
ebRequest.Headers.Authorization = new AuthenticationHeaderValue("Bearer", apitoken);
webRequest.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
Console.WriteLine(webRequest.RequestUri);
Console.WriteLine(webRequest.Headers.ToString());
var response = client.Send(webRequest);
In response to the duplicates, they seem to do an Async version which is different from the version shown below. I have added more code to show the difference.
The solution was the following:How to remove the default charset in HttpClient Request Header C#

Consider the following approach
content.Headers.Remove("Content-Type"); // "{application/json; charset=utf-8}"
content.Headers.Add("Content-Type", "application/json");

How do you send a certificate with an HttpRequestMessage?

Here I have an HttpRequestMessage, and I am trying to add a client certificate to it, but cannot seem to find how to do this. Has anyone out there done something like this?
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, "myapi/?myParm=" + aParm);
//Want to add a certificate to request - a .p12 file in my project
myAPIResponse res = await SendAndReadAsAsync<myAPIResponse>(request, aCancelToken);

Here is an answer combining HttpClient with HttpRequestMessage.
The HttpRequestMessage holding the data and client handling how the data is sent.
WebRequestHandler handler = new WebRequestHandler();
X509Certificate certificate = GetMyX509Certificate();
handler.ClientCertificates.Add(certificate);
HttpClient client = new HttpClient(handler);
var request = new HttpRequestMessage (HttpMethod.Get, "myapi/?myParm=" + aParm);
HttpResponseMessage response = await client.SendAsync (request);
response.EnsureSuccessStatusCode();
Edit: Here is a link explaining the difference between WebRequestHandler, HttpClientHandler & HttpClient to understand which one you should use when: https://learn.microsoft.com/en-us/archive/blogs/henrikn/httpclient-httpclienthandler-and-webrequesthandler-explained

HttpClient and Impersonation

From my web service (A) usng impersonation i would like call a WebAPI service (B) using HttpClient. But the service B always gets the system user of service A even though i do impersonation there.
var baseUri = "http://service/api/"
var handler = new HttpClientHandler { UseDefaultCredentials = true };
var client = new HttpClient(handler) { BaseAddress = baseUri };
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Add("ContentType", new List<string> { "application/json"});
var dataDto = new DataDto();
var json = JsonConvert.SerializeObject(dataDto );
var content = new StringContent(json);
content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
var response = await client.PostAsync(SubUrl, content);
I know that Kerberos and SPN are set up correctly because it works using WebClient.
I think the problem is, that HttpClient.PostAsync creates a new task and therefore a new thread running under the credentials of the appPool of service A.
Does anyone know how i could force the task to run under the imperonated credentials?
I do not have access to the aspnet_config.config so the solution proveded here does not work for me.
Thanks a lot!
Tschuege

HttpClient authentication header not getting sent

I'm trying to use an HttpClient for a third-party service that requires basic HTTP authentication. I am using the AuthenticationHeaderValue. Here is what I've come up with so far:
HttpRequestMessage<RequestType> request =
new HttpRequestMessage<RequestType>(
new RequestType("third-party-vendor-action"),
MediaTypeHeaderValue.Parse("application/xml"));
request.Headers.Authorization = new AuthenticationHeaderValue(
"Basic", Convert.ToBase64String(System.Text.ASCIIEncoding.ASCII.GetBytes(
string.Format("{0}:{1}", "username", "password"))));
var task = client.PostAsync(Uri, request.Content);
ResponseType response = task.ContinueWith(
t =>
{
return t.Result.Content.ReadAsAsync<ResponseType>();
}).Unwrap().Result;
It looks like the POST action works fine, but I don't get back the data I expect. Through some trial and error, and ultimately using Fiddler to sniff the raw traffic, I discovered the authorization header isn't being sent.
I've seen this, but I think I've got the authentication scheme specified as a part of the AuthenticationHeaderValue constructor.
Is there something I've missed?

Your code looks like it should work - I remember running into a similar problem setting the Authorization headers and solved by doing a Headers.Add() instead of setting it:
request.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(System.Text.ASCIIEncoding.ASCII.GetBytes(string.Format("{0}:{1}", "username", "password"))));
UPDATE:
It looks like when you do a request.Content, not all headers are being reflected in the content object. You can see this by inspecting request.Headers vs request.Content.Headers. One thing you might want to try is to use SendAsync instead of PostAsync. For example:
HttpRequestMessage<RequestType> request =
new HttpRequestMessage<RequestType>(
new RequestType("third-party-vendor-action"),
MediaTypeHeaderValue.Parse("application/xml"));
request.Headers.Authorization =
new AuthenticationHeaderValue(
"Basic",
Convert.ToBase64String(
System.Text.ASCIIEncoding.ASCII.GetBytes(
string.Format("{0}:{1}", "username", "password"))));
request.Method = HttpMethod.Post;
request.RequestUri = Uri;
var task = client.SendAsync(request);
ResponseType response = task.ContinueWith(
t =>
{ return t.Result.Content.ReadAsAsync<ResponseType>(); })
.Unwrap().Result;

This would also work and you wouldn't have to deal with the base64 string conversions:
var handler = new HttpClientHandler();
handler.Credentials = new System.Net.NetworkCredential("username", "password");
var client = new HttpClient(handler);
...

Try setting the header on the client:
DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(Encoding.ASCII.GetBytes(String.Format("{0}:{1}", userName, password))));
This works for me.

Also, consider that Redirect-Handler will clear the Authorization header if your request gets redirected.
So if you call an HTTP endpoint and it redirected to the HTTPS one, you will lose your authorization header.
request.Headers.Authorization = null;
Framework: .NET v6.0

Actually your problem is with PostAsync- you should use SendAsync. In your code - client.PostAsync(Uri, request.Content); sends only the content the request message headers are not included.
The proper way is:
HttpRequestMessage message = new HttpRequestMessage(HttpMethod.Post, url)
{
Content = content
};
message.Headers.Authorization = new AuthenticationHeaderValue("Basic", credentials);
httpClient.SendAsync(message);