Refit in C# — The API Client That Writes Itself (Almost)

I was recently asked to build an API that contacts two other APIs. My senior engineer casually dropped:

“Use Refit.”

At first, I was like — “what is this magic word?”
Then I used it. And I was pleasantly shocked.

🧠 What is Refit?

Think of Refit as your tiny API Copilot.

Refit is a REST library for .NET that turns your OpenAPI/Swagger spec into strongly-typed, auto-generated client code. Instead of manually writing a bunch of HttpClient logic, you describe your API once, and Refit generates the rest.

💥 Why It Blew My Mind

Here’s my flow:

I downloaded the Swagger JSON of the external Book API I needed to consume.

I created a refitter.yaml file with the configs.

Ran one CLI command.

And boom — Refit auto-generated:

• The interface with methods like GetBookByIdAsync
• The models like Book, Author, etc.
• The entire client logic, ready to use

Now I can just call:

var book = await _bookApi.GetBookByIdAsync(42);

No plumbing. No extra mapping. Clean.

🛠️ Installing & Using Refit (Quickstart)

Install Refit:

Install-Package Refit

Register the client in Program.cs:

services.AddRefitClient<IBookApi>()
        .ConfigureHttpClient(c => c.BaseAddress = new Uri("https://books.example.com"));

Use it like this:

public class LibraryService(IBook bookApi)
{
    public async Task<Book> FetchBook(int id)
    {
        return await bookApi.GetBookByIdAsync(id);
    }
}

🤔 Swagger: Your New Best Friend

Refit only works as well as your Swagger spec. A clean spec = clean client.
That realization made me treat Swagger not just as documentation, but as code — the contract between services.

When I polished the Swagger for my own API, downstream teams could just plug it into Refit and boom, done. That’s what future-proof API dev looks like.

🧩 Final Thoughts

We’re building an ecosystem where APIs and Kafka keep passing messages like trained athletes in a relay race. My role? Build one of those runners. But with Refit, I didn’t just build a runner — I gave it shoes, training, and a coach.

Whether you're a beginner dev or a product owner — Refit makes integrations faster, safer, and cleaner. All it asks for?
A good Swagger spec.