Question

For example:

class MyContoller
{
    [MyCustomAttribute]
    public ActionResult MyAction(ModelX fromRequest, ModelY fromSession, ModelZ fromCookie)
    {
       string productId = fromRequest.ProductId;
       string userId = fromSession.UserId;
       string cultureName = fromCookie.CultureName;
    }
}

Reason:

I don’t want to visit Request, Session and HttpContext in the controllers, and the default idea of MVC3 which passing models to actions is very great.

I want the number of parameters of MyAction is easy to change. For example, if I add a new parameter, the system will try to look for values in Request, Session or Cookies by the name or type of the parameter (I think custom ModelBinders may be required for cookie values) and pass the filled model to my action. I don’t have to write extra code.

Can the custom attribute (MyCustomAttribute in the example) accomplish this idea?

Answer 1

I am not sure I follow you about the custom attribute. What are you expecting the custom attribute to do?

Yes, an action method can take as many model parameters as you want. Obviously, only one can be bound in any given request (because a view can only have one model). Whichever one is found first will be bound, and the others will be null.

So let’s say you have the following:

public class ModelX {
    public string X {get;set;}
}

public class ModelY {
    public string Y {get;set;}
}

public class ModelZ {
    public string Z {get;set;}
}

And you have an action method like this:

public ActionResult DoIt(ModelX x, ModelY y, ModelZ z)
{
    return View();
}

And in your DoIt.cshtml you have the following:

@model ModelZ

@using(Html.BeginForm()) {
    @Html.TextBoxFor(x => x.Z)
    <input type="submit"/>
}

If you type something into the textbox and submit, then the model binder will bind a ModelZ with the value you entered and ModelX and ModelY will be null.

If you mean can an action method bind multiple models simultaneously, then I would have to ask you.. How exactly do you plan to have a view have more than one model? You can certainly create a wrapper model to contain the multiple models, but a view can only have one.