MVC Get Vs Post

Question

While going through MVC concepts, i have read that it is not a good practice to have code inside 'GET' action which changes state of server objects( DB updates etc.,). 'Caching of return data' has been given as a reason for this.

Could someone please explain this?

Thanks in advance!

Answer 1

This is by HTTP standard. The GET verb is one that should be idempotent and safe.

9.1.1 Safe Methods

Implementors should be aware that the software represents the user in their interactions over the Internet, and should be careful to allow the user to be aware of any actions they might take which may have an unexpected significance to themselves or others.

In particular, the convention has been established that the GET and HEAD methods SHOULD NOT have the significance of taking an action other than retrieval. These methods ought to be considered "safe". This allows user agents to represent other methods, such as POST, PUT and DELETE, in a special way, so that the user is made aware of the fact that a possibly unsafe action is being requested.

Naturally, it is not possible to ensure that the server does not generate side-effects as a result of performing a GET request; in fact, some dynamic resources consider that a feature. The important distinction here is that the user did not request the side-effects, so therefore cannot be held accountable for them.

http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html

Answer 2

Browsers can cache GET requests, generally on static data, like images or scripts. But you can also allow browsers to cache GET requests to controller actions as well, using [OutputCache] or other similar ways, so if caching is turned on for a GET controller action, it's possible that clicking on a link leading to /Home/Index doesn't actually run the Index method on the server, but rather allows the browser to serve up the page from its own cache.

With this line of thinking, you can safely turn on caching on GET actions in which the data you're serving up doesn't change (or doesn't change often), with the knowledge that your server action won't fire every time.

POSTs won't be cached by the browser, so any POST is guaranteed to make it to the server.