MVC - Best way to pass viewModel data from one controller (form) to another

I have two forms, PreRegister.html and Register.cshtml.  

PreRegister has a RadioButton group and I am trying to pass the user's selection - along with the CourseId that they had chosen to the Register controller/Form.

PreRegister.cshtml contains the following code:

 <div class="controls">
                    <label class="radio">
                        <input checked="checked" id="rbGrp" name="rbGrp" type="radio" value="1" /><label><b>Yes</b></label>
                       
                        <hr/>
                    </label>
                    <label class="radio">
                        <input id="rbGrp" name="rbGrp" type="radio" value="2" /><label><b>No</b></label>
                        
                    </label>
                </div>

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In my controller, I want to capture the user's selection plus the CourseId that had been passed into the PreRegister controller and then pass these values in an object to the full Register controller/form

This is what I have so far:

public ActionResult PreRegister(int id)
        {
            var viewModel = new RegistrationViewModel();
            {
                viewModel.Enrollment.CourseId = id;
            }
            return View(viewModel);
        }

        [HttpPost]
        public ActionResult PreRegister(RegistrationViewModel viewModel)
        {
            var enrollment = new Enrollment();
            enrollment.CourseId = viewModel.Enrollment.CourseId;
            enrollment.IsHdco = viewModel.Enrollment.IsHdco 
            //how to get IsHdco value from user selection of rbGrp?


            return RedirectToAction("Register", viewModel?? enrollment??);
            //how to pass the enrollment object over to Register?
        }

        public ActionResult Register(int id)
        {
            CodeCamper.Model.Course course = _coursesRepository.GetById(id);

            var viewModel = new PageContentViewModel();
            {
                viewModel.PageContent = course.Description;
                viewModel.Course = course;
            }

            return View(viewModel);
        }

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So I have 2 questions:
How do I get the value of the user selection from the radiobox group and translate it into a true/false?
How to I put this value plus CourseId into an object - either viewModel or Enrollment or something else and then transfer that as a parameter to the Register Controller that I want to geo to next?

Any help in figuring this out greatly appreciated.

RBS
RBSAsked:
Who is Participating?
 
Craig WagnerSoftware ArchitectCommented:
Because the radiobutton isn't part of your viewmodel you're going to have to use the FormCollection on your post method.

[HttpPost]
public ActionResult PreRegister(RegistrationViewModel viewModel, FormCollection formCollection)
{
    // formCollection["rbGrp"] will return "1" or "2" depending which radiobutton was selected
}

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As far as passing the information to another form action, you need to understand that what "RedirectToAction" is doing. Even though calling RedirectToAction looks like you're calling the new action directly, you aren't. Instead it is sending a 302 to the browser. The browser then requests the new URL. Given that understanding it becomes pretty clear there is really no way to directly pass the viewModel.

However, what MVC has given you is TempData. This uses the session state engine to preserve data across action redirects. So you would stuff whatever data you wanted to preserve into TempData and then pull it out in the new method.

[HttpPost]
public ActionResult PreRegister(RegistrationViewModel viewModel, FormCollection formCollection)
{
    TempData["SelectedRadioButton"] = formCollection["rbGrp"];
    TempData["SomeOtherValue"] = viewModel.SomeId;
    return RedirectToAction("Foo");
}

public ActionResult Foo()
{
    var selectedRadioButton =TempData["SelectedRadioButton"].ToString();
    var theId = (int)TempData["SomeOtherValue"]
}

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RBSAuthor Commented:
Thanks for this very clear explanation Craig with sample code.  One question arises - you said that "because the radiobutton isn't part of your model..."  

Is there an advantage of making a radiobutton part of my model?  Can you point to any resources that would explain how to do it or perhaps a sample line of code?  

Thanks again for your explanation!

RBS
0
 
Craig WagnerSoftware ArchitectCommented:
The advantage is that you get strong-typing in your model and you don't have to futz around with the FormCollection.

In the Model:

public class MyModel
{
    public string Choice { get; set; }
}

In the View:

@Html.RadioButtonFor( model => model.Choice, "1" )
@Html.RadioButtonFor( model => model.Choice, "2" )

In the Controller:

[HttpPost]
public ActionResult Foo( MyModel viewModel )
{
    if( viewModel.Choice == "2" )
    {
    }
    else if( viewModel.Choice == "1" )
    {
    }
}
0
 
RBSAuthor Commented:
Hi Craig:

A belated note to thank you for your additional explanation & code.  Clear and just what I needed.    Thanks,

RBS
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