If I do not specify [httpGet] or [httpPost] for the action method , what will be the rule for calling it

What I understand, By default It accept both type of request whether it is GET or POST. but when a action method is decorated with either [httpGet] or [httpPost] attribute then the action method accepts only those request method which define by attribute.

评论：

Assuming of course that you don't add one and not the other. For example, if you have the same action name, one with no attribute and the other with [HttpPost], then the one without an attribute is implicitly GET only.

– Chris Pratt

Oct 23 '14 at 17:24

ASP .NET MVC NonAction meaning

You can omit the NonAction attribute but then the method is still invokable as action method.

From the MSDN site (ref):

By default, the MVC framework treats all public methods of a controller class as action methods. If your controller class contains a public method and you do not want it to be an action method, you must mark that method with the NonActionAttribute attribute.

What is the default behaviour of a controller action not marked with AcceptVerbs, HttpGet or HttpPost?

It's accessible via any verb.

MVC [HttpPost/HttpGet] for Action

Let's say you have a Login action which provides the user with a login screen, then receives the user name and password back after the user submits the form:

public ActionResult Login() {
    return View();
}

public ActionResult Login(string userName, string password) {
    // do login stuff
    return View();
}

MVC isn't being given clear instructions on which action is which, even though we can tell by looking at it. If you add [HttpGet] to the first action and [HttpPost] to the section action, MVC clearly knows which action is which.

Why? See Request Methods. Long and short: When a user views a page, that's a GET request and when a user submits a form, that's usually a POST request. HttpGet and HttpPost just restrict the action to the applicable request type.

[HttpGet]
public ActionResult Login() {
    return View();
}

[HttpPost]
public ActionResult Login(string userName, string password) {
    // do login stuff
    return View();
}

You can also combine the request method attributes if your action serves requests from multiple verbs:

[AcceptVerbs(HttpVerbs.Get | HttpVerbs.Post)].