Purpose of ActionName

It is also useful if you have two Actions with the same signature that should have the same url.

A simple example:

public ActionResult SomeAction()
{
    ...
}

[ActionName("SomeAction")]
[HttpPost]
public ActionResult SomeActionPost()
{
    ...
}

It allows you to start your action with a number or include any character that .net does not allow in an identifier. - The most common reason is it allows you have two Actions with the same signature (see the GET/POST Delete actions of any scaffolded controller)

For example: you could allow dashes within your url action name http://example.com/products/create-product vs http://example.com/products/createproduct or http://example.com/products/create_product.

public class ProductsController {

    [ActionName("create-product")]
    public ActionResult CreateProduct() {
        return View();
    }

}