Reuse model data in a post action

Question

In my viewmodel, I have a list of items I fetch from the database and then send to the view. I would like to know if it's possible to avoid having to refill the options property whenever I hit a Post action and need to return the model (for validation errors and what not)?

In webforms, this wouldn't be necessary.

Edit: I was not clear. My problem is with the SelectList options I use for my DropDownLists. Everything gets posted, but if I have to return to the view (model is invalid), I have to reload the options from the database! I want to know if this can be avoided.

My viewmodel:

public class TestModel
{
    public TestModel()
    {
        Departments = new List<SelectListItem>();
    }

    public string Name { get; set; }
    public int Department { get; set; }
    public IEnumerable<SelectListItem> Departments { get; set; }
}

My view:

@model MvcApplication1.Models.TestModel    
@using (Html.BeginForm())
{
    @Html.TextBoxFor(m => m.Name)

    @Html.DropDownListFor(m => m.Department, Model.Departments)
    
    <input type=submit value=Submit />
}

My controller (do notice the comment on HttpPost):

public ActionResult Index()
{
    TestModel model = new TestModel
    {
        Name = "Rafael",
        Department = 1,
        Departments = new List<SelectListItem>
        {
            new SelectListItem { Text = "Sales", Value = "1" },
            new SelectListItem { Text = "Marketing", Value = "2", Selected = true },
            new SelectListItem { Text = "Development", Value = "3" }
        }
    };

    // Departments gets filled from a database.

    return View(model);
}

[HttpPost]
public ActionResult Index(TestModel model)
{
if (!ModelState.IsValid)
{
    //Do I have to fill model.Departments again!?!?!?
    
    return View(model); 
}
else { ...  }
}

Thanks in advance.

Edit: FYI, my solution was to use the Session variable.

Answer 1

Just need to strongly type your view, and change your controller method to have a parameter of that class type.

That is, the view

@model MyNamesspace.Models.MyModel
...
@using (Html.BeginForm())
{
    ....
}

And you controller method which is posted to.

[HttpPost]
public ActionResult MyAction(MyModel model)
{
    ...
}

EDIT: Also make sure you have form fields for each property of the model which you need posted to the controller. My example is using Razor too BTW.