Refit for C# (.NET): Type-safe REST Client

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1. What is it and why is it needed

Refit is an open-source library for the .NET platform that automatically generates HTTP client implementations based on interfaces described by the developer. It allows you to turn a regular C# interface into a full-fledged REST client, eliminating the need to manually write boilerplate code for making HTTP requests, JSON serialization/deserialization, and error handling.

The main problem that Refit solves is combating code duplication when working with REST APIs. Instead of creating a separate method with HttpClient for each endpoint, configuring headers, handling responses and exceptions, the developer simply declares an interface with methods marked with Refit attributes. The library itself generates the implementation using HttpClientFactory (recommended approach) or directly HttpClient.

Refit is especially useful when developing microservice architectures, integrating with third-party APIs (GitHub, Stripe, Telegram, etc.) and in any projects requiring type-safe interaction with HTTP services. It supports all major HTTP methods (GET, POST, PUT, DELETE, PATCH), working with headers, query parameters, request body, multipart forms, and files.

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2. Installation

Refit is distributed via NuGet. Use one of the following commands to install:

# Via .NET CLI\ndotnet add package Refit\n\n# Via Package Manager Console (Visual Studio)\nInstall-Package Refit\n\n# Or via NuGet Package Manager in IDE

For working with async methods and integration with ASP.NET Core, it is also recommended to install the Refit.HttpClientFactory package:

dotnet add package Refit.HttpClientFactory

If you are using System.Text.Json (default in .NET Core 3.1+), no additional packages are required. For Newtonsoft.Json, install Refit.Newtonsoft.Json.

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3. Quick Start — Minimal Working Example

Let's create a simple client for fetching data from JSONPlaceholder (a test REST API).

Step 1: Define the data model:

public class Todo\n{\n    public int Id { get; set; }\n    public int UserId { get; set; }\n    public string Title { get; set; }\n    public bool Completed { get; set; }\n}

Step 2: Create an interface with Refit attributes:

using Refit;\n\npublic interface ITodoApi\n{\n    [Get("/todos/{id}")]\n    Task<Todo> GetTodoAsync(int id);\n\n    [Get("/todos")]\n    Task<List<Todo>> GetAllTodosAsync();\n}

Step 3: Use Refit to create the client:

using Refit;\n\nclass Program\n{\n    static async Task Main(string[] args)\n    {\n        // Create client directly (without DI)\n        var todoApi = RestService.For<ITodoApi>("https://jsonplaceholder.typicode.com");\n        \n        // Get a single Todo\n        var todo = await todoApi.GetTodoAsync(1);\n        Console.WriteLine($"Todo: {todo.Title}, Completed: {todo.Completed}");\n        \n        // Get all Todos\n        var todos = await todoApi.GetAllTodosAsync();\n        Console.WriteLine($"Total todos: {todos.Count}");\n    }\n}

This example demonstrates the basic mechanics: you describe the interface, and Refit generates the implementation that performs HTTP requests and deserializes responses.

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