Lesson Wednesday

In this lesson, we'll discuss CRUD functionality and cover the remaining two HTTP methods: PATCH and DELETE. Together, the functionality offered by the full range of HTTP methods (GET, POST, PATCH and DELETE) is commonly referred to as CRUD in the industry.

HTTP Request Methods


CRUD stands for Create Read Update Delete. It's essentially shorthand for the full list of things we can do with objects in MVC programs. Each of these actions corresponds with a different HTTP method. Let's walk through each part of CRUD, and discuss the HTTP method that corresponds with each CRUD term. Some of this will be review:

GET

The Read Part of CRUD

GET requests information from the server, which is usually displayed to users. ASP.NET includes a HttpGet() method for GET requests.

POST

The Create Part of CRUD

POST alters information on the server. MVC has an HttpPost() method for POST requests. To create POST requests, we do three things:

  1. Add a method attribute of post to an HTML form.
  2. Add an action attribute with the intended path of the post request.
  3. Add a type attribute of submit to the form's button.

When the form is submitted, it will trigger a POST request.

In MVC, HTML forms without a method attribute of post are sent as GET requests instead. This is a common error!

PATCH

The Update Part of CRUD

PATCH also updates the server, but in a more specific manner than POST. PATCH updates existing information while POST usually adds entirely new data to the server.

For instance, if we update the caption of a photo we posted on Facebook, we're submitting a PATCH request. The photo already exists on their server and we're just updating one of the photo's attributes.

Here's a handy trick to remember the difference between POST and PATCH:

  • PATCH is like patching an old pair of jeans or a favorite quilt. The (well-loved) item already exists, we're just altering it.

  • POST is like posting to social media. That photo, tweet, or status didn't exist on their servers until you posted it. You're making something new!

DELETE

The Delete Part of CRUD

As its name suggests, DELETE removes data from the server. It, too, is like a more specific POST request. It does not add any new information and simply removes the specified data.

Visual Reference


It's a bit confusing that CRUD terms don't match the HTTP method names (besides DELETE). However, it'll become second-nature before too long. For now, here's a handy reference:

Limitations of HTML Forms


It's also important to understand the limitations of HTML forms. Primarily, HTML forms can only trigger GET and POST requests.

At one point, early drafts of HTML5 forms did support different requests. Those curious can see drafts from W3 here. (W3 is the World Wide Web Consortium. They develop standards for HTML and the web as a whole.) But support was later removed before HTML5's release.

Working Around HTML Limitations in MVC

.NET 5.0 does actually contain HttpPut() and HttpDelete() methods to define routes to handle these requests. However, we cannot trigger them using forms. Even a button that submits a request technically counts as an HTML form.

These methods are only included to create APIs, where other websites request data without forms or front-end user interfaces, so they don't encounter the same limitations. We'll be building APIs with ASP.NET later in this course.

Because HTML forms only execute GET and POST requests, we must use POST requests to update and/or delete records. This may feel hacky, but until HTML itself changes, it's the industry standard. We'll see how this works in the next few lessons.

CRUD stands for Create Read Update Delete.

GET requests information from the server, which is usually displayed to users. ASP.NET includes a HttpGet() method for GET requests.

POST alters information on the server. MVC has an HttpPost() method for POST requests.

PATCH updates existing information on the server.

DELETE removes data from the server.

We must use POST requests to update and delete records because HTML5 forms don't recognize PATCH AND DELETE.

Lesson 29 of 38
Last updated more than 3 months ago.