I have a ViewModel strongly bound to my View in my ASP.NET MVC app, now what about the controller

Question

So like the title says, I created a view model in my asp.net mvc application so it would be strongly typed to my view. My view model is a combination of two of my model classes. Now when the user hits the save button on that view, it goes to a controller. How does it know what controller to go to? I built my controller 1 - 1 so to speak with my models and views so controller A knows about Model A and controller B knows about Model B. But if I have a view model that is AB how does it know on subit to go to A or B. Do I need a controller called AB Controller?

Answer 1

The controller and action invoked do not depend on the viewmodel object you used to bind the page during initial view rendering. The controller (and action) invoked is determined by the URL of the request sent. (One of the routes you have defined will be matched based on the URL string of the request or a 404 not found error will be returned.)

A submit button in an HTML form (usually a POST) will have an action attribute that determines its url target, an anchor tag will have an href, etc.

In your situation where you have a custom viewmodel object you can define an action to expect and to attempt to parse that specific type of object by specifying it as the parameter to your action:

public ActionResult SaveSystemSetting(SystemAdminVM item) {

Answer 2

An Action Method doesn't receive a model. It receives parameters.

Anyway I think I know where you come from: One of the parameters of your action has the type of the ViewModel used in the View. That is a common layout and makes a lot of sense. In lots of projects it is so widely used that after some time you start to think that an action actually receives a model.

Just remenber that the parameters of your action can by anything that can by filled by the ModelBinder. You could pass both Models as parameters, you could pass a ViewModel that agregates Model a and b or you could pass a ViewModel that has properties of a + b. Agregation ist the most common approach.

Answer 3

Generally we overload our action methods in the controller so if you have an action called edit that renders the view with your viewmodel object, you will have an overloaded edit action method with the HttpPost specified for that method.

The data to this method will be passed as form value collection values or you can bind it to your viewmodel object if you like and process it further.