Understand CRUD

CRUD actions in ASP.NET Core

Our pizza service supports CRUD operations for a list of pizzas. These operations are performed through HTTP verbs, which are mapped via ASP.NET Core attributes.

The following table shows the mapping of the four operations that you're implementing for the pizza service:

HTTP action verb	CRUD operation	ASP.NET Core attribute
GET	Read	[HttpGet]
POST	Create	[HttpPost]
PUT	Update	[HttpPut]
DELETE	Delete	[HttpDelete]

You've already seen how GET actions work. Let's learn more about POST, PUT, and DELETE actions.

POST

To enable users to add a new item to the endpoint, you must implement the POST action by using the [HttpPost] attribute. When you pass the item (in this example, a pizza) into the method as a parameter, ASP.NET Core will automatically convert any application/JSON that's sent to the endpoint into a populated .NET Pizza object.

Here's the method signature of the Create method that you'll implement in the next section:

[HttpPost]
public IActionResult Create(Pizza pizza)
{            
    // This code will save the pizza and return a result
}

The [HttpPost] attribute will map HTTP POST requests sent to http://localhost:5000/pizza by using the Create() method. Instead of returning a list of pizzas, as we saw with the Get() method, this method returns an IActionResult response.

IActionResult lets the client know if the request succeeded and provides the ID of the newly created pizza. IActionResult does this by using standard HTTP status codes, so it can easily integrate with clients regardless of the language or platform they're running on.

ASP.NET Core action result	HTTP status code	Description
CreatedAtAction	201	The pizza was added to the in-memory cache. The pizza is included in the response body in the media type, as defined in the accept HTTP request header (JSON by default).
BadRequest is implied	400	The request body's pizza object is invalid.

Fortunately, ControllerBase has utility methods that will create the appropriate HTTP response codes and messages for you.

PUT

Modifying or updating a pizza in our inventory is similar to the POST method that you implemented, but it uses the [HttpPut] attribute and takes in the id parameter in addition to the Pizza object that needs to be updated:

[HttpPut("{id}")]
public IActionResult Update(int id, Pizza pizza)
{
    // This code will update the pizza and return a result
}

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
NoContent	204	The pizza was updated in the in-memory cache.
BadRequest	400	The request body's Id value doesn't match the route's id value.
BadRequest is implied	400	The request body's Pizza object is invalid.

DELETE

One of the easier actions to implement is the DELETE action, which takes in just the id parameter of the pizza to remove from the in-memory cache:

[HttpDelete("{id}")]
public IActionResult Delete(int id)
{
    // This code will delete the pizza and return a result
}

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
NoContent	204	The pizza was deleted from the in-memory cache.
NotFound	404	A pizza that matches the provided id parameter doesn't exist in the in-memory cache.

The exercise in the next unit demonstrates how to support each of the four actions in the web API.