How to connect a C# app to a REST API

One of the most useful modern C# skills is learning how to call an external API, read the returned data, and display it inside your application. In this beginner-friendly tutorial, you will use HttpClient and JSON deserialization to consume a public API.

LevelBeginner

FocusHttpClient + JSON

Project typeConnected app

What you will learn

Create a request with HttpClient
Receive JSON data from a web service
Map the JSON into a C# model class
Display the result in a Windows or console app

Step 1: Create your model class

Assume the API returns a JSON object with a title and a body. Create a class that matches the response shape.

public class Post
{
    public int userId { get; set; }
    public int id { get; set; }
    public string title { get; set; } = string.Empty;
    public string body { get; set; } = string.Empty;
}

Step 2: Call the API

Use HttpClient to send a GET request. Then convert the JSON response into a C# object.

using System.Net.Http;
using System.Text.Json;

var client = new HttpClient();
string url = "https://jsonplaceholder.typicode.com/posts/1";

string json = await client.GetStringAsync(url);
Post? post = JsonSerializer.Deserialize<Post>(json);

if (post != null)
{
    Console.WriteLine(post.title);
    Console.WriteLine(post.body);
}

Step 3: Display the data in your app

In a Windows Forms app, you could place the returned values inside labels, textboxes, or a dashboard card. In a console app, you can print them directly. The main lesson is that your C# application is now connected to an external data source.

Best practice: add error handling with try-catch and validate the response before displaying it to users.

Next improvements

Add a button so the user can fetch data on demand
Allow the user to enter an ID or keyword
Show multiple records in a grid or list
Connect to a weather, news, currency, or business API