Exercise - Add a controller

 A controller is a public class with one or more public methods known as actions. By convention, a controller is placed in the project root's Controllers directory. The actions are exposed as HTTP endpoints inside the web API controller.

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Create a controller

1. Select the Controllers folder in Visual Studio Code and add a new file called PizzaController.cs.

   

   An empty class file named PizzaController.cs is created in the Controllers directory. The Controllers directory name is a convention. The directory name comes from the model-view-controller architecture that the web API uses.

    Note

   By convention, controller class names are suffixed with Controller.

2. Add the following code to Controllers/PizzaController.cs. Save your changes.

   C#

   using ContosoPizza.Models;
   using ContosoPizza.Services;
   using Microsoft.AspNetCore.Mvc;
   
   namespace ContosoPizza.Controllers;
   
   [ApiController]
   [Route("[controller]")]
   public class PizzaController : ControllerBase
   {
       public PizzaController()
       {
       }
   
       // GET all action
   
       // GET by Id action
   
       // POST action
   
       // PUT action
   
       // DELETE action
   }
   

   As you learned previously, this class derives from ControllerBase, the base class for working with HTTP requests in ASP.NET Core. It also includes the two standard attributes you learned about: [ApiController] and [Route]. As before, the [Route] attribute defines a mapping to the [controller] token. Because this controller class is named PizzaController, this controller handles requests to https://localhost:{PORT}/pizza.

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Get all pizzas

The first REST verb that you need to implement is GET, where a client can get all pizzas from the API. You can use the built-in [HttpGet] attribute to define a method that returns the pizzas from our service.

Replace the // GET all action comment in Controllers/PizzaController.cs with the following code:

C#

[HttpGet]
public ActionResult<List<Pizza>> GetAll() =>
    PizzaService.GetAll();

The preceding action:

• Responds only to the HTTP GET verb, as denoted by the [HttpGet] attribute.
• Returns an ActionResult instance of type List<Pizza>. The ActionResult type is the base class for all action results in ASP.NET Core.
• Queries the service for all pizza and automatically returns data with a Content-Type value of application/json.

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Retrieve a single pizza

The client might also want to request information about a specific pizza instead of the entire list. You can implement another GET action that requires an id parameter. You can use the built-in [HttpGet("{id}")] attribute to define a method that returns the pizzas from our service. The routing logic registers [HttpGet] (without id) and [HttpGet("{id}")] (with id) as two different routes. You can then write a separate action to retrieve a single item.

Replace the // GET by Id action comment in Controllers/PizzaController.cs with the following code:

C#

[HttpGet("{id}")]
public ActionResult<Pizza> Get(int id)
{
    var pizza = PizzaService.Get(id);

    if(pizza == null)
        return NotFound();

    return pizza;
}

The preceding action:

• Responds only to the HTTP GET verb, as denoted by the [HttpGet] attribute.
• Requires that the id parameter's value is included in the URL segment after pizza/. Remember, the controller-level [Route] attribute defined the /pizza pattern.
• Queries the database for a pizza that matches the provided id parameter.

Each ActionResult instance used in the preceding action is mapped to the corresponding HTTP status code in the following table:

ASP.NET Core action result	HTTP status code	Description
Ok is implied	200	A product that matches the provided id parameter exists in the in-memory cache. The product is included in the response body in the media type, as defined in the accept HTTP request header (JSON by default).
NotFound	404	A product that matches the provided id parameter doesn't exist in the in-memory cache.

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Build and run the new controller

Build and start the web API by running the following command:

.NET CLI

dotnet run

Test the controller with an Http file

1. Open ContosoPizza.http

2. Add a new GET to call the Pizza endpoint under the ### seperator:

   Output

   GET {{ContosoPizza_HostAddress}}/pizza/
   Accept: application/json
   
   ###
   

3. Select the Send Request command above this new GET call.

   The preceding command returns a list of all pizzas in JSON:

   Output

   HTTP/1.1 200 OK
   Connection: close
   Content-Type: application/json; charset=utf-8
   Date: Wed, 17 Jan 2024 16:57:09 GMT
   Server: Kestrel
   Transfer-Encoding: chunked
   
   [
       {
           "id": 1,
           "name": "Classic Italian",
           "isGlutenFree": false
       },
       {
           "id": 2,
           "name": "Veggie",
           "isGlutenFree": true
       }
   ]   
   

4. To query for a single pizza, you can make another GET request, but pass in an id parameter by using the following command:

   Output

   GET {{ContosoPizza_HostAddress}}/pizza/1
   Accept: application/json
   
   ###
   

   The preceding command returns Classic Italian with the following output:

   Output

   HTTP/1.1 200 OK
   Content-Type: application/json; charset=utf-8
   Date: Fri, 02 Apr 2021 21:57:57 GMT
   Server: Kestrel
   Transfer-Encoding: chunked
   
   {
       "id": 1,
       "name": "Classic Italian",
       "isGlutenFree": false
   }
   

5. Our API also handles situations where the item doesn't exist. Call the API again, but pass in an invalid pizza id parameter by using the following command:

   Output

   GET {{ContosoPizza_HostAddress}}/pizza/5
   Accept: application/json
   
   ###
   

   The preceding command returns a 404 Not Found error with the following output:

   Output

   HTTP/1.1 404 Not Found
   Content-Type: application/problem+json; charset=utf-8
   Date: Fri, 02 Apr 2021 22:03:06 GMT
   Server: Kestrel
   Transfer-Encoding: chunked
   
   {
       "type": "https://tools.ietf.org/html/rfc7231#section-6.5.4",
       "title": "Not Found",
       "status": 404,
       "traceId": "00-ec263e401ec554b6a2f3e216a1d1fac5-4b40b8023d56762c-00"
   }
   

Now that you finished implementing the GET verbs. In the next unit, you can add more actions to PizzaController to support CRUD operations on pizza data.

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Optional: Test the controller with Command Line HTTP Read-Eval-Print Loop (REPL)

1. Open the existing httprepl terminal, or open a new integrated terminal from Visual Studio Code by selecting Terminal > New Terminal from the main menu.

2. Connect to our web API by running the following command:

   .NET CLI

   httprepl https://localhost:{PORT}
   

   Alternatively, run the following command at any time while HttpRepl is running:

   .NET CLI

   connect https://localhost:{PORT}
   

3. To see the newly available Pizza endpoint, run the following command:

   .NET CLI

   ls
   

   The preceding command detects all APIs available on the connected endpoint. It should display the following code:

   Output

    https://localhost:{PORT}/> ls
    .                 []
    Pizza             [GET]
    WeatherForecast   [GET]
   

4. Go to the Pizza endpoint by running the following command:

   .NET CLI

   cd Pizza
   

   The preceding command shows an output of available APIs for the Pizza endpoint:

   Output

   https://localhost:{PORT}/> cd Pizza
   /Pizza    [GET]
   

5. Make a GET request in HttpRepl by using the following command:

   .NET CLI

   get
   

   The preceding command returns a list of all pizzas in JSON:

   Output

     HTTP/1.1 200 OK
     Content-Type: application/json; charset=utf-8
     Date: Fri, 02 Apr 2021 21:55:53 GMT
     Server: Kestrel
     Transfer-Encoding: chunked
   
     [
         {
             "id": 1,
             "name": "Classic Italian",
             "isGlutenFree": false
         },
         {
             "id": 2,
             "name": "Veggie",
             "isGlutenFree": true
         }
     ]
   

6. To query for a single pizza, you can make another GET request, but pass in an id parameter by using the following command:

   .NET CLI

   get 1
   

   The preceding command returns Classic Italian with the following output:

   Output

   HTTP/1.1 200 OK
   Content-Type: application/json; charset=utf-8
   Date: Fri, 02 Apr 2021 21:57:57 GMT
   Server: Kestrel
   Transfer-Encoding: chunked
   
   {
       "id": 1,
       "name": "Classic Italian",
       "isGlutenFree": false
   }
   

7. Our API also handles situations where the item doesn't exist. Call the API again, but pass in an invalid pizza id parameter by using the following command:

   .NET CLI

   get 5
   

   The preceding command returns a 404 Not Found error with the following output:

   Output

   HTTP/1.1 404 Not Found
   Content-Type: application/problem+json; charset=utf-8
   Date: Fri, 02 Apr 2021 22:03:06 GMT
   Server: Kestrel
   Transfer-Encoding: chunked
   
   {
       "type": "https://tools.ietf.org/html/rfc7231#section-6.5.4",
       "title": "Not Found",
       "status": 404,
       "traceId": "00-ec263e401ec554b6a2f3e216a1d1fac5-4b40b8023d56762c-00"
   }
   

8. Return to the dotnet terminal in the drop-down list in Visual Studio Code and shut down the web API by selecting CTRL+C on your keyboard.

Now that you finished implementing the GET verbs. In the next unit, you can add more actions to PizzaController to support CRUD operations on pizza data.

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