Getting Started with Refit in .NET

Recap of Refit

Refit is the automatic type-safe REST library for .NET Core, Xamarin and .NET.

It lets you define your API calls using C# interfaces in simple three steps.

public interface IGitHubApi
{
    [Get("/users/{user}")]
    Task<User> GetUser(string user);
}
string url = "https://api.github.com";
var gitHubApi = RestService.For<IGitHubApi>(url);
var octocat = await gitHubApi.GetUser("octocat");
services.AddRefitClient<IGitHubApi>()
    .ConfigureHttpClient(c => c.BaseAddress = new Uri(url));

That is not the target for today’s newsletter, if you are not aware about how to use Refit in .NET then check this article I wrote earlier :

Using Refit to Consume APIs in .NET Core

👉 What Are Query Attributes and How to Add Them?

When you pass parameters in the query string of a URL, the parameters are appended to the URL after a question mark (?), and each parameter is specified as a key-value pair. Multiple parameters are separated by an ampersand (&). The general syntax is as follows:

http://example.com/path/to/resource?parameter1=value1

We can achieve similar in refit like this :

[Post("/api/student/details")]
Task<GetStudentDetailResponse> GetStudentDetailAsync(
    [Query] int studentId,
    GetStudentDetailCommand command,
    CancellationToken cancellationToken = default);

Parameter with [Query] would be passed as a query string and the one in command would be passed in body.

If you wish to add multiple parameters then add them and just add [Query] before that.

👉 How to Properly Set the Content Type Header

Content headers are essential, we need to set them with each request. Let me show you how would I add that.

I prefer to make a delegating handler for it, here you can read about it :

HTTP Message Handlers in ASP.NET Web API

public class AddDefaultContentHeader : DelegatingHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, 
        CancellationToken cancellationToken)
    {
        request.Headers.Add("Accept", "application/json");
        return await base.SendAsync(request, cancellationToken);
    }
}

services.AddRefitClient<IStudentRefitApi>(refitSettings)
    .ConfigureHttpClient(configureClient)
    .AddHttpMessageHandler<AddDefaultContentHeader>();

👉 How to Add Bearer Token in Headers

Similarly I can create a delegating handler for adding bearer token.

public sealed class AddBearerTokenHeader : DelegatingHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, 
        CancellationToken cancellationToken)
    {
        string token = "som-token"; 
        string bearerToken = $"Bearer {token}";
        request.Headers.Add("Authorization", bearerToken);
        return await base.SendAsync(request, cancellationToken);
    }
}

We can register it similarly as we did with content header. Add this handler only with your secure APIs which need token for successful call.