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Fluently Http Client

CircleCI NuGet version

Http Client for .NET Standard with fluent APIs which are intuitive, easy to use and also highly extensible.

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  • Fluent APIs
  • Highly extensible
  • Middleware Support
    • Custom Classes with DI enabled
    • Access to both Request/Response within same scope (similar to ASPNET middleware)
    • Logger and Timer middleware out of the box
  • Multiple HttpClient support with a Fluent API for Client builder
  • Customizable Formatters (JSON, XML out of the box)
  • Url interpolation and query params e.g. person/{id} / person?id=1
  • GraphQL support
  • File upload support


Available for .NET Standard 2.0+

NOTE: 1.x depends on .NET Standard 1.4+, use that if you need older .NET standard.


PM> Install-Package FluentlyHttpClient


<PackageReference Include="FluentlyHttpClient" Version="*" />

Table of Contents



Add services via .AddFluentlyHttpClient().

// using Startup.cs (can be elsewhere)
public void ConfigureServices(IServiceCollection services)

Configure an Http client using the Http Factory (you need at least one).

// using Startup.cs (can be elsewhere)
public void Configure(IApplicationBuilder app, IFluentHttpClientFactory fluentHttpClientFactory)
  fluentHttpClientFactory.CreateBuilder(identifier: "platform") // keep a note of the identifier, its needed later
    .WithBaseUrl("") // required
    .WithHeader("user-agent", "slabs-testify")
    .Register(); // register client builder to factory

Basic usage

Simple API

Simple API (non-fluent) is good for simple requests as it has a clean, minimal API.

// inject factory and get client
var httpClient = fluentHttpClientFactory.Get(identifier: "platform");

// HTTP GET + deserialize result (non-fleunt API)
Hero hero = await httpClient.Get<Hero>("/api/heroes/azmodan");

// HTTP POST + deserialize result (non-fleunt API)
Hero hero = await httpClient.Post<Hero>("/api/heroes/azmodan", new
        Title = "Lord of Sin"

Fluent Request API

Fluent request API (request builder) allows to create more complex requests and provides further control on the response.

// inject factory and get client
var httpClient = fluentHttpClientFactory.Get(identifier: "platform");

// HTTP GET + return response and deserialize result (fluent API)
FluentHttpResponse<Hero> response = 
  await httpClient.CreateRequest("/api/heroes/azmodan")
    .ReturnAsResponse<Hero>(); // return with response

// HTTP POST + return response and deserialize result (fluent API)
Hero hero = await httpClient.CreateRequest("/api/heroes/azmodan")
        Title = "Lord of Sin"
    .Return<Hero>(); // return deserialized result directly

Fluent Http Client Builder

Http client builder is used to configure http clients in a fluent way.

Register to Factory

var clientBuilder = fluentHttpClientFactory.CreateBuilder(identifier: "platform")

// or similarly via the builder itself.

Register multiple + share

There are multiple ways how to register multiple http clients. The following is a nice way of doing it:

    // shared
    .WithHeader("user-agent", "slabs-testify")

    // platform

    // big-data - reuse all above and replace the below

Create Http Client from Client

Its also possible to create a new http client from an http client, sort of sub-client which inherits options from its creator. This might be good to pass defaults for a specific endpoint.

var httpClient = factory.Get("platform");
var paymentsClient = httpClient.CreateClient("payments")
  .WithHeader("X-Gateway", "xxx")

Configure defaults for Http Clients

Its also possible to configure builder defaults for all http clients via ConfigureDefaults within IFluentHttpClientFactory. See example below.

    => builder.WithUserAgent("sketch7")

Http Client Builder extra goodies

// message handler - set HTTP handler stack to use for sending requests
var mockHttp = new MockHttpMessageHandler();

// request builder defaults - handler to customize defaults for request builder
httpClientBuilder.WithRequestBuilderDefaults(builder => builder.AsPut());

// formatters - used for content negotiation, for "Accept" and body media formats. e.g. JSON, XML, etc...
httpClientBuilder.ConfigureFormatters(opts =>
      opts.Default = new MessagePackMediaTypeFormatter();
      opts.Formatters.Add(new CustomFormatter());

Re-using Http Client from Factory

As a best practice rather than using a string each time for the identifier, it's better to create an extension method for it.

public static class FluentHttpClientFactoryExtensions
    public static IFluentHttpClient GetPlatformClient(this IFluentHttpClientFactory factory)
        => factory.Get("platform");

Request Builder

Request builder is used to build http requests in a fluent way.


LoginResponse loginResponse =
  await fluentHttpClient.CreateRequest("/api/auth/login")
    .AsPost() // set as HTTP Post
        Username = "test",
        Password = "test"
    }) // serialize body content
    .WithSuccessStatus() // ensure response success status
    .Return<LoginResponse>(); // send, deserialize result and return result directly.

Query params

        Take = 5,
        Roles = new List<string> { "warrior", "assassin" },
    }, opts => {
        opts.CollectionMode = QueryStringCollectionMode.CommaSeparated;
        opts.KeyFormatter = key => key.ToLower();
    }); // => /url?roles=warrior,assassin&take=5

Interpolate Url

requestBuilder.WithUri("{Language}/heroes/{Hero}", new
        Language = "en",
        Hero = "azmodan"
    }); // => /en/heroes/azmodan

ReturnAsReponse, ReturnAsResponse<T> and Return<T>

// send and returns HTTP response
FluentHttpResponse response = requestBuilder.ReturnAsResponse();

// send and returns HTTP response + deserialize and return result via `.Data`
FluentHttpResponse<Hero> response = requestBuilder.ReturnAsResponse<Hero>();

// send and returns derserialized result directly
Hero hero = requestBuilder.Return<Hero>();


FluentlyHttpClient ❤️ GraphQL. First class support for GraphQL to be able to create request/response even simpler.

// configure globally to use uri for GraphQL endpoint.
httpClientBuilder.WithRequestBuilderDefaults(requestBuilder => requestBuilder.WithUri("api/graphql"));

// send and returns HTTP response + deserialize and return result via `.Data` directly
FluentHttpResponse<Hero> response =
  await fluentHttpClient.CreateGqlRequest("{ hero {name, title } }")
    // => response.Data.Title


Middleware's are used to intercept request/response to add additional logic or alter request/response.

Implementing a middleware for the HTTP client is quite straight forward, and it's very similar to ASP.NET Core middleware.

These are provided out of the box:

Middleware Description
Timer Determine how long (timespan) requests takes.
Logger Log request/response.

Two important points to keep in mind:

  • The first argument within constructor has to be FluentHttpMiddlewareDelegate which is generally called next.
  • The second argument within constructor has to be FluentHttpMiddlewareClientContext which is generally called context,
  • During Invoke the await _next(context); must be invoked and return the response, in order to continue the flow.

The following is the timer middleware implementation (bit simplified).

public class TimerHttpMiddleware : IFluentHttpMiddleware
    private readonly FluentHttpMiddlewareDelegate _next;
    private readonly TimerHttpMiddlewareOptions _options;
    private readonly ILogger _logger;

    public TimerHttpMiddleware(
      FluentHttpMiddlewareDelegate next, // this needs to be here and should be first
      FluentHttpMiddlewareClientContext context, // this needs to be here and should be second
      TimerHttpMiddlewareOptions options,
      ILoggerFactory loggerFactory
        _next = next;
        _options = options;
        _logger = loggerFactory.CreateLogger($"{typeof(TimerHttpMiddleware).Namespace}.{context.Identifier}.Timer");

    public async Task<FluentHttpResponse> Invoke(FluentHttpMiddlewareContext context)
        var watch = Stopwatch.StartNew();
        var response = await _next(context); // this needs to be invoked to continue middleware flow
        var elapsed = watch.Elapsed;
        _logger.LogInformation("Executed request {request} in {timeTakenMillis}ms", context.Request, elapsed.TotalMilliseconds);
        return response;

namespace FluentlyHttpClient
    // Response extension methods - useful to extend FluentHttpResponse
    public static class TimerFluentResponseExtensions
        private const string TimeTakenKey = "TIMER_TIME_TAKEN";

        public static void SetTimeTaken(this FluentHttpResponse response, TimeSpan value)
          => response.Items.Add(TimeTakenKey, value);

        public static TimeSpan GetTimeTaken(this FluentHttpResponse response)
          => (TimeSpan)response.Items[TimeTakenKey];

    // FluentHttpClientBuilder extension methods - add
    public static class FluentlyHttpMiddlwareExtensions
        public static FluentHttpClientBuilder UseTimer(this FluentHttpClientBuilder builder, TimerHttpMiddlewareOptions options = null)
            => builder.UseMiddleware<TimerHttpMiddleware>(options ?? new TimerHttpMiddlewareOptions());

// response extension usage
TimeSpan timeTaken = response.GetTimeTaken();

Middleware options

Options to middleware can be passed via an argument. Note it has to be the second argument within the constructor.

public TimerHttpMiddleware(
  FluentHttpMiddlewareDelegate next,
  FluentHttpMiddlewareClientContext context,
  TimerHttpMiddlewareOptions options, // <- options should be here
  ILoggerFactory loggerFactory

Options can be passed when registering a middleware.

Use a middleware

    .UseMiddleware<LoggerHttpMiddleware>() // register a middleware (without args)
    .UseMiddleware<TimerHttpMiddleware>(new TimerHttpMiddlewareOptions
          WarnThreshold = TimeSpan.Zero
      }) // register a middleware with options (args)
    .UseTimer(new TimerHttpMiddlewareOptions
          WarnThreshold = TimeSpan.Zero
      }) // register a middleware using extension method

As a best practice, it's best to provide an extension method for usage such as UseTimer especially when it has any arguments (options), as it won't be convenient to use.

Request/Response items

When using middleware additional data can be added to the request/response via the .Items of request/response, in order to share state across middleware for the request or to extend response.

The timer middleware example is making use of it.

// set item

// or similarly without extension method
response.Items.Add("TIME_TAKEN", value)

// get item
TimeSpan timeTaken = response.GetTimeTaken();

// or similarly without extension method
TimeSpan timeTaken = (TimeSpan)response.Items["TIME_TAKEN"];


One of the key features is the ability to extend its own APIs easily. In fact, several functions of the library itself are extensions, by using extension methods.

Extending Request Builder

An example of how can the request builder be extended.

public static class FluentHttpRequestBuilderExtensions
    public static FluentHttpRequestBuilder WithBearerAuthentication(this FluentHttpRequestBuilder builder, string token)
        if (string.IsNullOrEmpty(token)) throw new ArgumentNullException(nameof(token));
        builder.WithHeader("Authorization", $"Bearer {token}");
        return builder;

Extending Request Builder/Client Builder headers

In order to extend headers for both FluentHttpClientBuilder and FluentHttpRequestBuilder, the best approach would be to extend on IFluentHttpHeaderBuilder<T>, this way it will be available for both. See example below.

public static class FluentHttpHeaderBuilderExtensions
  public static T WithBearerAuthentication<T>(this IFluentHttpHeaderBuilder<T> builder, string token)
    if (string.IsNullOrEmpty(token)) throw new ArgumentNullException(nameof(token));
    builder.WithHeader(HeaderTypes.Authorization, $"{AuthSchemeTypes.Bearer} {token}");
    return (T)builder;

Extending Request/Response items

In order to extend Items for both FluentHttpRequest and FluentHttpResponse, its best to extend IFluentHttpMessageState. This way it will be available for both. See example below.

public static IDictionary<string, string> GetErrorCodeMappings(this IFluentHttpMessageState message)
  if (message.Items.TryGetValue(ErrorCodeMappingKey, out var value))
    return (IDictionary<string, string>)value;
  return null;


File upload

var multiForm = new MultipartFormDataContent
  { "hero", "Jaina" }
multiForm.AddFile("file", "./animal-mustache.jpg");

var response = await httpClient.CreateRequest("/api/sample/upload")

Simple Single file HttpClient

Even though in general we do not suggest (unless for small HttpClients) at times its useful to create a simple quick way http client.

public class SelfInfoHttpClient
  private readonly IFluentHttpClient _httpClient;

  public SelfInfoHttpClient(
    IFluentHttpClientFactory httpClientFactory
    _httpClient = httpClientFactory.CreateBuilder("localhost")

  public Task<FluentHttpResponse> GetInfo()
    => _httpClient.CreateRequest("info")


In order to test HTTP requests, the library itself doesn't offer anything out of the box. However, we've been using RichardSzalay.MockHttp, which we recommend.

Test example with RichardSzalay.MockHttp

public async void ShouldReturnContent()
    // build services
    var servicesProvider = new ServiceCollection()
    var fluentHttpClientFactory = servicesProvider.GetService<IFluentHttpClientFactory>();

    // define mocks
    var mockHttp = new MockHttpMessageHandler();
      .Respond("application/json", "{ 'name': 'Azmodan' }");

    var httpClient = fluentHttpClientFactory.CreateBuilder("platform")
      .WithMessageHandler(mockHttp) // set message handler to mock

    var response = await httpClient.CreateRequest("/api/heroes/azmodan")

    Assert.Equal("Azmodan", response.Data.Name);
    Assert.NotEqual(TimeSpan.Zero, response.GetTimeTaken());


Setup Machine for Development

Install/setup the following:

  • NodeJS v8+
  • Visual Studio Code or similar code editor
  • Git + SourceTree, SmartGit or similar (optional)


# run tests
npm test

# bump version
npm version minor --no-git-tag # major | minor | patch | prerelease

# nuget pack (only)
npm run pack

# nuget publish dev (pack + publish + clean)
npm run publish:dev

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