Redirect after save in partial views

Question

Say the requirement is to redirect to another page after successfully saving a model in an ASP.NET MVC controller:

[HttpPost]
public ActionResult Index(ViewModel viewModel)
{
   if (ModelState.IsValid)
   {
        // Do save;

        return RedirectToAction("whatever"); // <--- here's the problem 
    }

    // display validation errors and so
    return View(viewModel);
}

This would work fine unless the controller was rendered as a Child Action:

@{
    Layout = "my layout";

    Html.RenderAction("something else, a view for example");
    Html.RenderAction("Index action of the above controller"); // <----
}

In this case RedirectResult class would check and see that the context is a child action and would throw the exception: "Child actions are not allowed to perform redirect actions".

I understand that writing to Response stream is already in progress and a redirect cannot take place here but nevertheless one has to be able to redirect to other pages after a server-side action in a controller even if that action is a child action. We use Layouts and RenderActions to reuse the shared parts of the page design.

How would you implement such a redirect in such a controller?

Edit:

The main goal is to reuse View/Controllers that do a specific job and split them to logical concepts like displaying some data or providing an edit form. My approach here is to use RenderAction to render their result into a container. Container view (main page's Index action) acts as a traditional asp.net Page, its Layout view as a Master page and edit and view controller/views are equivalent to User Controls (modules). The problem is there is no way to Redirect the Response after something has been written to it:

Answer 1

I'll submit a new answer in an attempt to keep things clean.
A normal mvc flow goes like this :
Http command reaches 1 controller which acts as a choirmaster(aka controller) and calls several logic containers(e.g services / commandHandlers) :

public ActionResult Index(){
  var data = _yourService.FetchData();
  return View(data);
}

This controller renders 1 view which can have multiple partials

@{
    Layout = "my layout";
}
<p>Some html</p>
Html.RenderPartial("A shared partial");
Html.RenderPartial("shared\yourUserControl", Model.PropertyOrSomething);

If the partial contains too much logic to generate you could add a RenderAction or create an htmlHelper extension.
But neither of these should be able to control the flow of your request, a save or something that can redirect should in my opinion never be called from inside a view.
I assume you want to reuse the code in your controller so badly because it is getting quite big.
My advice would be to try and clear that controller up as much as possible by delegating as much of the logic upwards as you can.
Just by looking at your controller method for 5 seconds you should get an idea of what this action will do, if that's not the case : refactor it ! :)

Answer 2

If i understand correctly you have a parent controller which accepts a saveAction and while rendering the view you call another(?) saveAction as a child.
This flow feels unnatural to me.
The parent action and only the parent action should handle the save command.
You can render as many child actions as you want as long as they are only used to render some html(as this is what the view does).
Don't let them handle redirection or saving, that way of working is everything but transparant for colleges or future you.
The controller controls the flow, not the view.

Edit:
A normal setup would be having 2 actions, eg: Index and Put.

public ActionResult Index(){
  //fill model with dropdown data etc
  return View();
} 

public ActionResult Put(viewModel data){
   if (ModelState.IsValid)
   {
        // Do save;
        return RedirectToAction("whatever"); // <--- here's the problem 
    }

    // display validation errors and so
    return View("Index",viewModel);
}

Edit2: If you return View("Index",viewModel) you will generate your index view with it's layout and the validation messages will be located in the modelstate.
Your view however should only have 1 childaction(or more if there are multiple, as long as it's not the save action). Your Index view could look like this :

@{
    Layout = "my layout";
}
Html.RenderAction("something else, a view for example");
@Html.BeginForm("Put","YourController"){
  //all your input controls which will also show the validation errors
}

Edit 3: If you want to reuse html code you should use @Html.Partial or Html helper extension methods. Note that if you pass no model the parents model is passed but you can pass a submodel to match the type safety of the partial.

It would look something like this :

@{
    Layout = "my layout";
}
Html.RenderAction("something else, a view for example");
Html.RenderPartial("shared\yourUserControl", Model.PropertyOrSomething);

Answer 3

Try using AJAX in your view to do this, and instead of returning a RedirectToAction in your controller, return a JSON object:

View:

 $.ajax({
            url: '<%: Html.ResolveUrl("~/ControllerFolder/ControllerName/") %>',
            type: "POST",
            data: data,
            success: function (result) {
                $("#Div").html(result);
                if (result.redirectUrl != null) 
                {
                    window.location = result.redirectUrl;
                }
            }   

        });

Controller:

 [HttpPost]
public ActionResult Index(ViewModel viewModel)
{
   if (ModelState.IsValid)
   {
        // Do save;

        return Json(new { redirectUrl = Url.Action("NewAction", "NewController", RouteValues)}); 
    }

    // display validation errors and so
    return View(viewModel);
}

Hope this helps...