How to "hook" into the pipe where the argument/object gets passed to the action-method

Question

Is there any way to alter the passed object to an action-method before it actually enters/(gets passed to) the action-metod?.. For instance... By default I want the Index()-action-method to always take an argument of MyClass..

So.. if a user visit mydomain.com/AController/

The triggerd action-method should be

public ActionResult Index(MyClass arg)
{ 
    return View();
}

Im not really sure of how to explain this.. but hopefully you get it.. What I actually want to do is the same thing that Umbraco does in thier MVC-project.. where they always pass-along a RenderModel-object, except that I want to have my own type not the RenderModel..

Thanks in advance!

Forgive me if I overlook your Umbraco remarks, but you might be missing the point of the model binding you get in ASP.NET MVC. You can use an Action Filter to hook into the pipeline, but it's not clear whether you want to *add* the "RenderModel" or if the RenderModel *is your model*. Can you elaborate and show us what `MyClass` looks like and maybe an example of RenderModel? — David Fox, Oct 18 '13 at 12:21
By using an action filter I guess you mean something like: [MyActionFilter] public ActionResult Index(MyClass arg) { return View() } ?, this is not an option.. I dont want to use any decoration-attributes.. just "simply" modify the pipe before the Index action-method gets executed so it gets executed with the parameter args as an object of type MyClass — Inx, Oct 18 '13 at 12:42

score 1 · Accepted Answer · answered Oct 18 '13 at 13:20

1

As I understand your question, you want your action being invoked with a default arg value (if none is provided)

Considering your MyClass as :

public class MyClass 
{
    public int Id { get; set; }
    public string Name { get; set; }
}

You may define your route like :

        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{arg}",
            defaults: new { controller="Home",
                            action = "Index", 
                            arg = new MyClass() { Id = 1, Name = "test" } 
                      }
        );

I guess another option would be to have a custom ModelBinder or, at lower level, a custom ValueProvider.

answered Oct 18 '13 at 13:20

jbl

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Yes.. this could be an option.. hmm.. ModelBinder you say.. or ValueProvider.. you dont happen to know any good reading regarding this?.. guess I could google it.. but all recommendations are very welcome :) – Inx Oct 18 '13 at 14:20
@Inx my reading is the paper book "ASP.NET MVC 4 in Action" ( http://www.manning.com/palermo3/ ) It features a whole chapter on ModelBinders and ValueProviders using the Session as backend for ValueProvider. A really nice book – jbl Oct 18 '13 at 20:00

Digbyswift · Answer 2 · 2013-10-22T17:43:24.123

Provided your class is simple enough, there should be no need to intercept the call to the action.

For example, if the class has a properties of int, string and DateTime, even IEnumerable<int> etc, then MVC will map form post data or a querystring to the class automatically.

So, a URL like example.com/your-path/?id=1&categories=3,4,56&tags=this,that would automatically map to a class like:

public YourClass
{
    public int Id { get; set; }
    public IEnumerable<int> Categories { get; set; }
    public IEnumerable<string> Tags { get; set; }
}

If you need to do additional work with the data, for example, if you are posting XML/JSON and need to deserialize it before populating your class, then @jbl's answer is the one for you.

From an Umbraco perspective, if you are hijacking your controllers, then you could simply add your class to the Index() action as an additional parameter, e.g. Index(RenderModel model, YourClass arg). This would pick up and populate any additional data pass to your page.

The problem with @jbl's approach with Umbraco is that Umbraco handles the routing for you, so you can not specify your own routing without bypassing Umbraco's controllers entirely - which defeats the purpose of using Umbraco :)

How to "hook" into the pipe where the argument/object gets passed to the action-method

2 Answers2