Cannot Send GET Request with Content-Type Header with RestSharp v107

[PierreCollardSuero]

After upgrading to v107, I started getting the following error when trying to execute a GET request with the Content-Type: application/force-download header:
Cannot send a content-body with this verb-type.

The header is the only parameter in the request, but it seems like RestSharp transparently adds a body causing the error.

All attempts below causes the error mentioned when executing the request:
restRequest.AddHeader("Content-Type", "application/force-download");
restRequest.Parameters.AddParameter(new BodyParameter("", "", "application/force-download", DataFormat.None));
restRequest.AddStringBody("", "application/force-download");

While it may not be a good practice to use this header parameter with a GET request, it is unfortunately required for me to perform some operation with a system from a vendor and the last version of RestSharp does not support this anymore.

[alexeyzimarev]

Hm, right now the content-type header is added to the content, and if there's no content, there's no header set. There was an issue about it here and I implemented the proposed change to add an empty body.

It is not RestSharp that fails the request, it's the particular implementation of HttpClient. I bet you are on .NET < 5?

[PierreCollardSuero]

Yes, I am using .NET Framework 4.8. Is there a way to work with HttpClient to implement a workaround instead of upgrading the .NET version?

[alexeyzimarev]

I saw a question on SO about setting the content type header, it looks like it can be set on the request itself. I will look into it.

[PierreCollardSuero]

Microsoft recommends to extend a .NET Framework application with a .NET one rather than migrating it entirely to .NET which makes sense as it would be a lot of work:
https://docs.microsoft.com/en-us/dotnet/standard/choosing-core-framework-server

I don't know how long it can take for this issue to be closed so I built a .NET 6 project that includes a class that uses RestSharp v107 to try and resolve my issue.

However, a .NET project cannot be referenced from a .NET Framework one.
I believe a .NET Standard (and maybe a .NET Core) project can be referenced by a .NET Framework one, but I'm not sure if switching to .NET Standard 2.1 or .NET Core 3.1 would fix my issue with RestSharp.

What do you suggest me to do?

• Give you more time (if so, would it be possible to get an ETA?)
• Build a .NET Standard/Core library
• Revert to RestSharp v106
• etc.

[alexeyzimarev]

.NET Standard is just an API surface, it doesn't have any implementation. It will use the underlying SDK API, so if you reference a .NET Standard package in .NET 4.8 project, it will use .NET 4.8.

[alexeyzimarev]

Check this one: https://stackoverflow.com/questions/26109650/explicitly-set-content-type-headers-for-get-operation-in-httpclient

Basically, it's not an exception produced by RestSharp, it's what HttpClient does, so if you use HttpClient directly, you will get the same issue. The workaround using a delegating handler is equally applicable for RestSharp as you can supply a delegating handler in client options.

[alexeyzimarev]

I made this code:

        var options = new RestClientOptions("https://enlgqo6062j5.x.pipedream.net/");
        var client  = new RestClient(options);

        var request = new RestRequest("resource");
        request.AddHeader("Content-Type", "application/force-download");
        var response = await client.GetAsync(request);

Tried with .NET 6 and .NET Framework 4.8 and both worked. Could you create a repro repository and share it here?

[alexeyzimarev]

That's how the request looks like:

[alexeyzimarev]

Btw RestSharp for .NET Standard doesn't include any reference to System.Net.Http, which you'd need to add yourself. I tested it with 4.3.4 and it worked, maybe it's an easy fix for you actually to update the package version.

[alexeyzimarev]

I added a test for it targeting .NET Framework 4.8 and it passes on my machine (macOS) but fails in the CI pipeline (Windows). So, it's not only framework-specific, it is also platform-specific.

I tried to add the Content-Type header to the request itself and got this:

System.InvalidOperationException
Misused header name. Make sure request headers are used with HttpRequestMessage, response headers with HttpResponseMessage, and content headers with HttpContent objects.

Honestly, I don't think it's possible with HttpClient. If you know how to avoid these exceptions, please add a comment here.

[VictorRH]

I made this code:

        var options = new RestClientOptions("https://enlgqo6062j5.x.pipedream.net/");
        var client  = new RestClient(options);

        var request = new RestRequest("resource");
        request.AddHeader("Content-Type", "application/force-download");
        var response = await client.GetAsync(request);

Tried with .NET 6 and .NET Framework 4.8 and both worked. Could you create a repro repository and share it here?

I have error with "content-type", "application/x-www-form-urlencoded"

old source code

var client = new RestClient("urSite") {
  Timeout = -1,
  Proxy = clientProxy
  };
var request = new RestRequest(Method.POST);
request.AddHeader("accept", "application/json");
request.AddHeader("accept-language", "en-US,en;q=0.9");
request.AddHeader("content-type", "application/x-www-form-urlencoded");
request.AddHeader("origin", "url");
request.AddHeader("referer", "ur;");
client.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36";
request.AddParameter("application/x-www-form-urlencoded",$"body",ParameterType.RequestBody);

var response = await client.ExecuteAsync(request);

and this is new version

var options = new RestClientOptions(token.Url) {
Proxy = proxy,
  UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36"
};
var request = new RestClient(options);
var postPayload = new RestRequest {
	Method = Method.Post,
};
postPayload.AddHeader("accept", "application/json");
postPayload.AddHeader("accept-language", "en-US,en;q=0.9");
postPayload.AddHeader("content-type", "application/x-www-form-urlencoded");
postPayload.AddHeader("origin", "urlorigin");
postPayload.AddHeader("referer", "urlReferer");
postPayload.AddParameter("application/x-www-form-urlencoded", token.PostPayload, ParameterType.RequestBody);
var response = await request.ExecuteAsync(postPayload);

and receive error 

`'Misused header name, 'content-type'. Make sure request headers are used with HttpRequestMessage, response headers with HttpResponseMessage, and content headers with HttpContent objects.'`

I using net core 6 web api in windows

[PierreCollardSuero]

I managed to apply a fix with a utility class using System.Net.HttpClient directly.
The implementation might be too dirty for many, but the usage is very simple and clean:

// using System.Net.Http;
// using System.Net.Http.Headers;
// using System.Linq;
// using System.Threading;
// using System.Threading.Tasks;
// using System.Collections.Generic;
// using System.Reflection;
// using RestSharp;

public static class HttpMessageUtils
{
    public const string ContentTypeHeaderName = "Content-Type";

    class HandlerAllowingContentTypeHeaderOnGetRequests : DelegatingHandler
    {
        public HandlerAllowingContentTypeHeaderOnGetRequests(
            HttpMessageHandler p_innerHttpMessageHandler
        ) : base(p_innerHttpMessageHandler)
        { }

        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage p_request, CancellationToken p_cancellationToken)
        {
            FieldInfo invalidHeadersField =
                typeof(HttpHeaders).GetField("invalidHeaders", BindingFlags.NonPublic | BindingFlags.Instance) ??   // System.Net.Http v2.2+
                typeof(HttpHeaders).GetField("_invalidHeaders", BindingFlags.NonPublic | BindingFlags.Instance)     // System.Net.Http before v2.2
            ;

            HashSet<string> invalidHeaders = (HashSet<string>)invalidHeadersField.GetValue(p_request.Headers);

            if (invalidHeaders.Contains(ContentTypeHeaderName))
            {
                invalidHeaders.Remove(ContentTypeHeaderName);

                string contentTypeHeaderValue = p_request.Content.Headers.ContentType.MediaType;
                string requestContent = await p_request.Content.ReadAsStringAsync();

                if (string.IsNullOrWhiteSpace(requestContent))
                    p_request.Content = null;
                else
                    p_request.Content.Headers.Remove(ContentTypeHeaderName);

                p_request.Headers.Add(ContentTypeHeaderName, contentTypeHeaderValue);
            }

            HttpResponseMessage response = await base.SendAsync(p_request, p_cancellationToken);
            return response;
        }
    }

    public static HttpClient GetHttpClient(this RestClient p_restClient)
    {
        return ((TypeInfo)p_restClient.GetType())
            .DeclaredProperties
            .First(p => p.Name == "HttpClient")
            .GetValue(p_restClient)
            as HttpClient
        ;
    }

    private static FieldInfo GetHttpMessageHandlerField(this HttpClient p_httpClient)
    {
        return ((TypeInfo)p_httpClient.GetType().BaseType)
            .DeclaredFields
            .First(f => f.Name == "handler")
        ;
    }

    public static HttpMessageHandler GetMessageHandler(this HttpClient p_httpClient)
    {
        return p_httpClient.GetHttpMessageHandlerField()
            .GetValue(p_httpClient)
            as HttpMessageHandler
        ;
    }

    public static void SetMessageHandler(this HttpClient p_httpClient, HttpMessageHandler p_newHttpMessageHandler)
    {
        p_httpClient.GetHttpMessageHandlerField().SetValue(p_httpClient, p_newHttpMessageHandler);
    }

    public static HttpMessageHandler GetInnerMessageHandler(this RestClient p_restClient)
    {
        return p_restClient.GetHttpClient().GetMessageHandler();
    }

    public static void AllowContentTypeHeaderOnGetRequests(this RestClient p_restClient)
    {
        HttpMessageHandler innerMessageHandler = p_restClient.GetInnerMessageHandler();
        HttpMessageHandler newMessageHandler = new HandlerAllowingContentTypeHeaderOnGetRequests(innerMessageHandler);
        p_restClient.GetHttpClient().SetMessageHandler(newMessageHandler);
    }
}

RestClientOptions restClientOptions = new(p_baseURL) { Credentials = p_credentials };
RestClient restClient = new(restClientOptions);
RestRequest restRequest = new(p_relativeResourcePath, p_method);

restRequest.AddHeader("Content-Type", "application/force-download");
restClient.AllowContentTypeHeaderOnGetRequests();
RestResponse restResponse = await restClient.ExecuteAsync(restRequest, p_method);

[alexeyzimarev]

@VictorRH I wrote in the docs that you should not set the content type header manually. Please read the docs.