Passing data from a View to a Controller in .NET MVC - "@model" not highlighting

Question

The following code works as I need it to:

 @using (Html.BeginForm("LOLOL", "PATIENT", null))
    {
        @Html.ValidationSummary(true)
        <fieldset>
            <legend>PATIENT</legend>
            <div class="editor-label">
                @Html.LabelFor(model => model.Name)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.Name)
                @Html.ValidationMessageFor(model => model.Name)
            </div>

        </fieldset>
        <p>
            <input type="submit" value="SUBMIT" />
        </p>
    }  

In LOLOLController:

[HttpPost]
    public IActionResult LOLOL(Patient p) {
        var client = new MongoClient("mongodb://localhost:27017");
        var userId = _userManager.GetUserId(HttpContext.User);
        string db_name = "test" + userId;
        var database = client.GetDatabase(db_name);
        var collection = database.GetCollection<BsonDocument>("patients");
        var filter = Builders<BsonDocument>.Filter.Eq("Name", p.Name.ToString());
        var document = collection.Find(filter).First();
        // I'm cutting short the rest of the code, because when I do something 
 // similar later, "collection.Find(filter).First()" fires an exception, I'll     
// explain..


        return View(p);
    }

I have something equivalent to taking off the fieldset element in the HTML, leaving basically just a button in the "Html.BeginForm", but then the data is clearly not binding properly, which I know because if I just have a button and no data-entry, I click the button and then I get an error saying the data cannot be found from the database. (EDIT: I now have confirmed that this is indeed because the Patient object is not being passed to the controller quite as I expected it to, seems like a brand new Patient object was created upon calling html.beginform ... I thought that maybe the old Patient object was being passed so I did not have to enter all its data members every time we use Html.BeginForm)

In sum, I want to fill out a text box, click a button to load a new page and display the value of that textbox, but have that value also persisted in essentially a session state, so that if I call another Html.BeginForm function and go into a third view, the text from the first view will be displayed in the third view, even though I did not have to type its value in the second view. Hopefully I can repeat this process, and essentially load up the data members of a class with one view per data member.

Answer 1

Make sure you pass the data from the previous view to the new view from your Controller. When you pass it, include @HiddenFor for those properties from the previous view in your new view. That way the new view will keep and then pass the values to your next POST.

@Html.HiddenFor(model => model.PropertyYouPassedAndWantToKeepAndPassAgain

Edit: Here's the logic for using multiple views for one object... as requested.

Model:

public class Patient
{
    string Name { get; set; }
    string Address { get; set; }
    string City { get; set; }
}

Page1 GET:

[HttpGet]
public ActionResult Page1()
{
    Patient patient = new Patient();
    return View("~/Views/Page1.cshtml", patient);
}

Page 1 View... only ask for the name.

@model mysite.Models.Patient

@using (Html.BeginForm("LOLOL", "PATIENT", null))
    {
        @Html.ValidationSummary(true)
        <fieldset>
            <legend>PATIENT</legend>
            <div class="editor-label">
                @Html.LabelFor(model => model.Name)
            </div>
            <div class="editor-field">
                @Html.EditorFor(model => model.Name)
                @Html.ValidationMessageFor(model => model.Name)
            </div>

        </fieldset>
        <p>
            <input type="submit" value="SUBMIT" />
        </p>
    }

Page1 POST... get the patient and pass it on to the next view...

[HttpPost]
public ActionResult Page1(Patient patient)
{
    if (ModelState.IsValid)
    {
        return View("~/Views/Page2.cshtml", patient); // pass your patient to the second page view with the name
    }
    else
    {
        return View("~/Views/Page1.cshtml", patient);
    }
}

Page2 GET... get the patient from the prior Page1 POST and send it off to the Page2 View.

[HttpGet]
public ActionResult Page2(Patient patient)
    {
        // Receive patient from Page1 post and pass it to new view... includes the name
        return View("~/Views/Page2.cshtml", patient);
    }

Page2 View gets the object... use a HiddenFor to keep the name which you just sent from the GET.

@model mysite.Models.Patient

@using (Html.BeginForm("LOLOL", "PATIENT", null))
{
    @Html.HiddenFor(model => model.Name) @* This will keep the name on your next post *@
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>PATIENT</legend>
        <div class="editor-label">
            @Html.LabelFor(model => model.Address)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Address)
            @Html.ValidationMessageFor(model => model.Address)
        </div>

    </fieldset>
    <p>
        <input type="submit" value="SUBMIT" />
    </p>
}

Since the HiddenFor holds the Name, it will be passed on your next post. It is there but hidden from the form itself.

[HttpPost]
public ActionResult Page2(Patient patient)
{
    // Because of the HiddenFor, the Name will be passed because it was kept in the view... but hidden from the form itself.
    // It's basically storing it for you to pass again
    if (ModelState.IsValid)
    {
        // Pass object with Name and Address to next controller
        return View("~/Views/Page3.cshtml", patient);
    }
    else
    {
        return View("~/Views/Page2.cshtml", patient);
    }
}

Page2 POST

[HttpPost]
public ActionResult Page2(Patient patient)
{
    // Because of the HiddenFor, the Name will be passed because it was kept in the view... but hidden from the form itself.
    // It's basically storing it for you to pass again
    if (ModelState.IsValid)
    {
        // Pass object with Name and Address to next controller
        return View("~/Views/Page3.cshtml", patient);
    }
    else
    {
        return View("~/Views/Page2.cshtml", patient);
    }
}

Page3 GET

[HttpGet]
public ActionResult Page3(Patient patient)
{
    // Pass patient again... to your next view
    return View("~/Views/Page3.cshtml", patient);
}

Page3 View...

@using (Html.BeginForm("LOLOL", "PATIENT", null))
{
    @Html.HiddenFor(model => model.Name) @* Keep name again for your next post *@
    @Html.HiddenFor(model => model.Address) @* Now we are keeping the address as well *@
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>PATIENT</legend>
        <div class="editor-label">
            @Html.LabelFor(model => model.City)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.City)
            @Html.ValidationMessageFor(model => model.City)
        </div>

    </fieldset>
    <p>
        <input type="submit" value="SUBMIT" />
    </p>
} 

And so on and so forth... until you have your model complete and want to do something with it.