Best pratice for completing MVC model properties which aren't bound? - asp.net-mvc-4

Question

I am trying to find the best way to use MVC for models which are only partially edited.
Below is an simple example.
Model
using System.ComponentModel.DataAnnotations;
public class SimpleModel
{
public int Id { get; set; }
public string Parent { get; set; }
[Required]
public string Name { get; set; }
}
View
using System.ComponentModel.DataAnnotations;
public class SimpleModel
{
public int Id { get; set; }
public string Parent { get; set; }
[Required]
public string Name { get; set; }
}
Controller
using System.Web.Mvc;
public class SimpleController : Controller
{
public ActionResult Edit(int id)
{ return View(Get(id)); }
[HttpPost]
public ActionResult Edit(int id, SimpleModel model)
{
if (model.Name.StartsWith("Child")) //Some test that is not done client-side.
{
Save(model);
//Get the saved data freshly.
//model = Get(id);
}
else
{
ModelState.AddModelError("", "Name should start with 'Child'");
}
//Is this the way to set the Parent property?
//var savedModel = Get(id);
//model.Parent = savedModel.Parent;
return View(model);
}
//Mock a database.
SimpleModel savedModel;
private void Save(SimpleModel model)
{ savedModel = new SimpleModel() { Id = model.Id, Name = model.Name }; }
private SimpleModel Get(int id)
{
if (savedModel == null)
{ return new SimpleModel() { Id = id, Parent = "Father", Name = "Child " + id.ToString() }; }
else
{ return new SimpleModel() { Id = savedModel.Id, Parent = "Father", Name = savedModel.Name }; }
}
}
The Name field is editable. The Parent field is only for reference and should not be updated. Therefore, it is rendered using DisplayFor.
Upon post, I receive a model with property Parent set to null. That's no problem as it will not be saved. However, when I simply return the received model to the view, the Parent field will no longer be displayed. When the model is valid, I can easily get it again from the database and thus get the Parent field's value back.
When the model is not valid, I would like to allow the user to correct input and attempt to save once more. There, I the received model's values that are input should be used, but the displayed values should be shown as well.
In reality, there are many more fields to be shown for reference, most often from different database entities than the one that is being edited.
I have seen suggestions to pass the fields as hidden fields in the view, but I feel very reluctant to read data from the client that should not be updated.
Is there a more elegant way to do this than copying these values into the model manually or passing them as hidden fields?

Answer 1

What about giving those un-editable properties to another model and let it take care of those properties?
View Model
public class PersonViewModel
{
public int Id { get; set; }
[Required]
public string FirstName { get; set; }
[Required]
public string LastName { get; set; }
public PersonDetailsModel DetailsModel { get; set; }
}
Details Model
public class PersonDetailsModel
{
public string Mother { get; set; }
public string Father { get; set; }
public PersonDetailsModel() { }
public PersonDetailsModel(int personId)
{
// pull required model data from databases
var db = DBParentContext;
Mother = db.Parent.Where(m => m.ChildId == personId)
Father = db.Parent.Where(m => m.ChildId == personId)
}
}
Controller
public class PersonController : Controller
{
[HttpPost]
public ActionResult Edit(PersonViewModel viewModel)
{
viewModel.DetailsModel = new PersonDetailsModel(viewModel.Id)
if (ModelState.IsValid) {
// ~
}
return View(viewModel)
}
}
View
#model PersonViewModel
#Html.DisplayFor(m => m.DetailsModel.Mother)
#Html.DisplayFor(m => m.DetailsModel.Father)
#Html.TextBoxFor(m => m.FirstName)
#Html.TextBoxFor(m => m.LastName)
Since details like your Mother are un-editable then they're not really part of the "Edit" model, so I'd box like that away and try to let something else take care of them.

Answer 2

If you aren't going to update the Parent field, then it really doesn't matter if it's a hidden or not, since you won't update it on post.
I would use the hidden in this case, just make sure not to update that field.