REST API

Introduction

REST (Representational State Transfer) is a popular architectural style for building APIs. In this tutorial, we will cover how to create and consume REST APIs using .NET. We will create a RESTful service and a client to consume this service.

Prerequisites

Visual Studio installed with .NET development workload
Basic knowledge of .NET and C#

Creating a RESTful Service

First, create a new RESTful service project in Visual Studio:

Open Visual Studio and click "Create a new project".
Select "ASP.NET Core Web Application" and click "Next".
Set the name and location for your project and click "Create".
Choose "API" as the template and click "Create".

Defining the Data Model

Define your data model by creating a new class:

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
}

Creating the Controller

Create a new controller to handle API requests:

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using System.Linq;

namespace MyApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class PersonsController : ControllerBase
    {
        private static List<Person> persons = new List<Person>
        {
            new Person { Id = 1, Name = "John Doe", Age = 30 },
            new Person { Id = 2, Name = "Jane Doe", Age = 25 }
        };

        [HttpGet]
        public ActionResult<IEnumerable<Person>> Get()
        {
            return persons;
        }

        [HttpGet("{id}")]
        public ActionResult<Person> Get(int id)
        {
            var person = persons.FirstOrDefault(p => p.Id == id);
            if (person == null)
            {
                return NotFound();
            }
            return person;
        }

        [HttpPost]
        public ActionResult<Person> Post([FromBody] Person person)
        {
            persons.Add(person);
            return CreatedAtAction(nameof(Get), new { id = person.Id }, person);
        }

        [HttpPut("{id}")]
        public IActionResult Put(int id, [FromBody] Person updatedPerson)
        {
            var person = persons.FirstOrDefault(p => p.Id == id);
            if (person == null)
            {
                return NotFound();
            }
            person.Name = updatedPerson.Name;
            person.Age = updatedPerson.Age;
            return NoContent();
        }

        [HttpDelete("{id}")]
        public IActionResult Delete(int id)
        {
            var person = persons.FirstOrDefault(p => p.Id == id);
            if (person == null)
            {
                return NotFound();
            }
            persons.Remove(person);
            return NoContent();
        }
    }
}

Running the Service

Run the service by pressing F5 or clicking the "Start" button in Visual Studio. The API will be available at https://localhost:5001/api/persons.

Creating a REST Client

Now, create a new .NET Console App to consume the REST API:

Open Visual Studio and click "Create a new project".
Select "Console App (.NET Core)" and click "Next".
Set the name and location for your project and click "Create".

Consuming the REST API

Modify the Program.cs file to call the REST API:

using System;
using System.Net.Http;
using System.Net.Http.Json;
using System.Threading.Tasks;

namespace MyRestClient
{
    class Program
    {
        static async Task Main(string[] args)
        {
            using var client = new HttpClient();

            // GET all persons
            var persons = await client.GetFromJsonAsync<Person[]>("https://localhost:5001/api/persons");
            foreach (var person in persons)
            {
                Console.WriteLine($"{person.Id} - {person.Name} - {person.Age}");
            }

            // GET person by id
            var personById = await client.GetFromJsonAsync<Person>("https://localhost:5001/api/persons/1");
            Console.WriteLine($"{personById.Id} - {personById.Name} - {personById.Age}");

            // POST a new person
            var newPerson = new Person { Id = 3, Name = "Sam Smith", Age = 40 };
            var response = await client.PostAsJsonAsync("https://localhost:5001/api/persons", newPerson);
            Console.WriteLine($"Created: {response.StatusCode}");

            // PUT to update a person
            newPerson.Name = "Samuel Smith";
            response = await client.PutAsJsonAsync("https://localhost:5001/api/persons/3", newPerson);
            Console.WriteLine($"Updated: {response.StatusCode}");

            // DELETE a person
            response = await client.DeleteAsync("https://localhost:5001/api/persons/3");
            Console.WriteLine($"Deleted: {response.StatusCode}");
        }
    }

    public class Person
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
    }
}

Running the Client

Run the client application by pressing F5 or clicking the "Start" button in Visual Studio. You should see the details of the persons retrieved from the REST API and the results of the POST, PUT, and DELETE operations.

Conclusion

In this tutorial, we covered how to create and consume REST APIs with .NET. You learned how to define a data model, implement the service in .NET, and consume the service with a .NET client application. REST provides a simple and standardized way to work with APIs, making it easy to build and consume web services. Happy coding!