DXA Custom Controller losing the MvcData on HttpPost

Question

I have a custom Form Controller in a DXA 1.2 web application that is working fine at request time but when I post the form data back to that Controller and return the Entity DXA throws an error as it has lost the MvcData for my custom controller.

ERROR - Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'.
System.Web.HttpException (0x80004005): Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'. ---> System.InvalidOperationException: The view 'Index' or its master was not found or no view engine supports the searched locations. The following locations were searched:
~/Views/Form/Index.aspx
~/Views/Form/Index.ascx
~/Views/Shared/Index.aspx
~/Views/Shared/Index.ascx
~/Views/Form/Index.cshtml
~/Views/Form/Index.vbhtml
~/Views/Shared/Index.cshtml
~/Views/Shared/Index.vbhtml
   at System.Web.Mvc.ViewResult.FindView(ControllerContext context)

Controller code:

public class FormController : EntityController
{
    [HandleSectionError(View = "SectionError")]
    public ActionResult Index(EntityModel entity, int containerSize = 0)
    {
        // The List action is effectively just an alias for the general Entity action (we keep it for backward compatibility).
        return Entity(entity, containerSize);
    }

    [HttpPost]
    public ActionResult Index(Form form)
    {
        //do stuff here and modify the success flag
        form.SubmittedSuccessfully = true;
        return Entity(form);
    }
}

Is there anyway to re-populate this data?

Answer 1

This really isn't to my liking but without any other code examples of how to do this I have had to place the MvcData in TempData

protected override ViewModel EnrichModel(ViewModel model)
{
    var form = model as Form;
    TempData["MvcData"] = form.MvcData;
    return base.EnrichModel(model);
}

Then the Form Controller picks up the post and then I re-create the MvcData using the value in TempData

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Index(Form form)
{
    form.MvcData = TempData["MvcData"] as MvcData;
    //do some business logic here
    form.SubmittedSuccessfully = true;
    return Entity(form);
}

Answer 2

The easiest way to achieve what you want may be to let the form submit itself using an HTTP GET to URL of the Page containing the Form.

In that manner, the built-in Page Controller will handle the form submit (PageController.Page). It will delegate its work to Region Controllers and Entity Controllers. If one of the Entities on the Page is a Form (with associated FormController), the FormController.EnrichModel method will be invoked.

So, you should override the EnrichModel method in the Form Controller and there you will have access to the form data (in Query String Parameters). See, for example, the ListController.EnrichModel override.

If you really have to use an HTTP POST, I guess the built-in PageController.Page method can't be used. In that case you will have to create your own (Page) Controller and give it a similar implementation as PageController.Page. I would recommend to let your Controller inherit from PageController and let your action method delegate to PageController.Page.