Refitter

Refitter is a CLI tool for generating a C# REST API Client using the Refit library. Refitter can generate the Refit interface from OpenAPI specifications

Installation:

The tool is packaged as a .NET Tool and is published to nuget.org. You can install the latest version of this tool like this:

dotnet tool install --global Refitter

Usage:

$ refitter --help

USAGE:
    refitter [input file] [OPTIONS]

EXAMPLES:
    refitter ./openapi.json --namespace "Your.Namespace.Of.Choice.GeneratedCode" --output ./Output.cs

ARGUMENTS:
    [input file]    Path to OpenAPI Specification file

OPTIONS:
                                      DEFAULT                                                          
    -h, --help                                         Prints help information                         
    -n, --namespace                   GeneratedCode    Default namespace to use for generated types    
    -o, --output                      Output.cs        Path to Output file                             
        --no-auto-generated-header                     Don't add <auto-generated> header to output file
        --interface-only                               Don't generate contract types                   

To generate code from an OpenAPI specifications file, run the following:

$ refitter [path to OpenAPI spec file] --namespace "[Your.Namespace.Of.Choice.GeneratedCode]"

This will generate a file called Output.cs which contains the Refit interface and contract classes generated using NSwag

Using the generated code

Here's an example generated output from the Swagger Petstore example

using Refit;
using System.Threading.Tasks;
using System.Collections.Generic;

namespace Your.Namespace.Of.Choice.GeneratedCode
{
    public interface ISwaggerPetstore
    {
        /// <summary>
        /// Update an existing pet by Id
        /// </summary>
        [Put("/pet")]
        Task<Pet> UpdatePet([Body]Pet body);

        /// <summary>
        /// Add a new pet to the store
        /// </summary>
        [Post("/pet")]
        Task<Pet> AddPet([Body]Pet body);

        /// <summary>
        /// Multiple status values can be provided with comma separated strings
        /// </summary>
        [Get("/pet/findByStatus")]
        Task<ICollection<Pet>> FindPetsByStatus([Query]Status? status);

        /// <summary>
        /// Multiple tags can be provided with comma separated strings. Use tag1, tag2, tag3 for testing.
        /// </summary>
        [Get("/pet/findByTags")]
        Task<ICollection<Pet>> FindPetsByTags([Query(CollectionFormat.Multi)]ICollection<string> tags);

        /// <summary>
        /// Returns a single pet
        /// </summary>
        [Get("/pet/{petId}")]
        Task<Pet> GetPetById(long? petId);

        [Post("/pet/{petId}")]
        Task UpdatePetWithForm(long? petId, [Query]string name, [Query]string status);

        [Delete("/pet/{petId}")]
        Task DeletePet(long? petId);

        [Post("/pet/{petId}/uploadImage")]
        Task<ApiResponse> UploadFile(long? petId, [Query]string additionalMetadata, [Body]StreamPart body);

        /// <summary>
        /// Returns a map of status codes to quantities
        /// </summary>
        [Get("/store/inventory")]
        Task<IDictionary<string, int>> GetInventory();

        /// <summary>
        /// Place a new order in the store
        /// </summary>
        [Post("/store/order")]
        Task<Order> PlaceOrder([Body]Order body);

        /// <summary>
        /// For valid response try integer IDs with value <= 5 or > 10. Other values will generated exceptions
        /// </summary>
        [Get("/store/order/{orderId}")]
        Task<Order> GetOrderById(long? orderId);

        /// <summary>
        /// For valid response try integer IDs with value < 1000. Anything above 1000 or nonintegers will generate API errors
        /// </summary>
        [Delete("/store/order/{orderId}")]
        Task DeleteOrder(long? orderId);

        /// <summary>
        /// This can only be done by the logged in user.
        /// </summary>
        [Post("/user")]
        Task CreateUser([Body]User body);

        /// <summary>
        /// Creates list of users with given input array
        /// </summary>
        [Post("/user/createWithList")]
        Task<User> CreateUsersWithListInput([Body]ICollection<User> body);

        [Get("/user/login")]
        Task<string> LoginUser([Query]string username, [Query]string password);

        [Get("/user/logout")]
        Task LogoutUser();

        [Get("/user/{username}")]
        Task<User> GetUserByName(string username);

        /// <summary>
        /// This can only be done by the logged in user.
        /// </summary>
        [Put("/user/{username}")]
        Task UpdateUser(string username, [Body]User body);

        /// <summary>
        /// This can only be done by the logged in user.
        /// </summary>
        [Delete("/user/{username}")]
        Task DeleteUser(string username);
    }
}

RestService

Here's an example usage of the generated code above

using Refit;
using System;
using System.Threading.Tasks;

namespace Your.Namespace.Of.Choice.GeneratedCode;

internal class Program
{
    private static async Task Main(string[] args)
    {
        var client = RestService.For<ISwaggerPetstore>("https://petstore3.swagger.io/api/v3");
        var pet = await client.GetPetById(2);

        Console.WriteLine($"Name: {pet.Name}");
        Console.WriteLine($"Category: {pet.Category.Name}");
        Console.WriteLine($"Status: {pet.Status}");
    }
}

The RestService class generates an implementation of ISwaggerPetstore that uses HttpClient to make its calls.

The code above when run will output something like this:

Name: Gatitotototo
Category: Chaucito
Status: Sold

ASP.NET Core and HttpClientFactory

Here's an example Minimal API with the Refit.HttpClientFactory library:

using Refit;
using Your.Namespace.Of.Choice.GeneratedCode;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services
    .AddRefitClient<ISwaggerPetstore>()
    .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://petstore3.swagger.io/api/v3"));

var app = builder.Build();
app.MapGet(
        "/pet/{id:long}",
        async (ISwaggerPetstore petstore, long id) =>
        {
            try
            {
                return Results.Ok(await petstore.GetPetById(id));
            }
            catch (Refit.ApiException e)
            {
                return Results.StatusCode((int)e.StatusCode);
            }
        })
    .WithName("GetPetById")
    .WithOpenApi();

app.UseHttpsRedirection();
app.UseSwaggerUI();
app.UseSwagger();
app.Run();

.NET Core supports registering the generated ISwaggerPetstore interface via HttpClientFactory

The following request to the API above

$ curl -X 'GET' 'https://localhost:5001/pet/1' -H 'accept: application/json'

Returns a response that looks something like this:

{
  "id": 1,
  "name": "Special_char_owner_!@#$^&()`.testing",
  "photoUrls": [
    "https://petstore3.swagger.io/resources/photos/623389095.jpg"
  ],
  "tags": [],
  "status": "Sold"
}

System requirements

.NET 7.0

For tips and tricks on software development, check out my blog

If you find this useful and feel a bit generous then feel free to buy me a coffee ☕