ASP.NET MVC DropDownListFor Model binding - asp.net-mvc

Question

I am trying to bind a dropdown to my model, but I am having issues. My model that is passed into my HttpPost function is NULL, but only if I try to bind to the "product" object's CategoryID field. If I exclude trying to bind to product.CatgeoryID, then the IncidentNumber string is not null. Thanks for any input.
Here is my model.
public class BIFireTypeModel
{
public int ID { get; set; }
public string Name { get; set; }
}
public class Product
{
public int CategoryID { get; set; }
public Product()
{
CategoryID = 0;
}
}
And here is my controller:
//
// GET: /BasicIdentification/
[HttpGet]
public ViewResult BasicIdentificationIndex()
{
Product newproduct = new Product();
ViewModelData vmd = new ViewModelData();
vmd.product = newproduct;
vmd.product.CategoryID = 2;
ViewBag.Categories = GetItems();
return View(vmd);
}
[HttpPost]
public ActionResult BasicIdentificationIndex(ViewModelData product)
{
ViewBag.Categories = GetItems();
return View(product);
}
public List<BIFireTypeModel> GetItems()
{
List<BIFireTypeModel> categories = new List<BIFireTypeModel>();
categories.Add(new BIFireTypeModel() { ID = 1, Name = "IA" });
categories.Add(new BIFireTypeModel() { ID = 2, Name = "Extended Attack" });
categories.Add(new BIFireTypeModel() { ID = 3, Name = "Large Fire Support" });
return categories;
}
public class ViewModelData
{
public String IncidentNumber { get; set; }
public Product product { get; set; }
}
And finally my cshtml:
#{
using (Html.BeginForm())
{
<h4>Incident Number</h4><input id="txtIncidentNumber" name="IncidentNumber" type="text" />
#Html.DropDownListFor(x => x.product.CategoryID, new SelectList(ViewBag.Categories, "ID", "Name"))
#* WILL CAUSE IncidentNumber in BasicIdentificationIndex(ViewModelData product) TO BE NULL
<h4>Incident Number</h4><input id="afasf" name="product.CategoryID" type="text" />
*#
<input type="submit" value="Submit" />
}
}
EDIT
In my Post function, I can access product.CategoryID with Request[] like so:
[HttpPost]
public ActionResult BasicIdentificationIndex(ViewModelData product)
{
String tmp = Request["product.CategoryID"];
ViewBag.Categories = GetItems();
return View(product);
}
And it returns the right value. But this value will not bind in my model, and if I try to use DropDownListFor at all with product, ALL VALUES in ViewModelData product will be null.

Answer 1

FIXED:
Here is the issue.
public ActionResult BasicIdentificationIndex(ViewModelData product)
public class ViewModelData
{
public Employee product { get; set; }
}
The NAME of my object in my ViewModelData was the same as the PARAMETER in BasicIdentificationIndex(). This caused major issues. All I had to do was change the name.
EDIT:
Something else that is very IMPORTANT is that when I was using EditorForModel(), my dropdowns weren't binding, but when I would manually create them with #Html.EnumDropDownListFor the binding worked. Good to know.

Answer 2

Here is an example approach that populates three DropDownListFor at the same View:
ViewModel:
public class GroupViewModel
{
public IEnumerable<SelectListItem> Schedules { get; set; }
public int ScheduleId { get; set; }
public IEnumerable<SelectListItem> Labs { get; set; }
public int LabId { get; set; }
public IEnumerable<SelectListItem> Terms { get; set; }
public int TermId { get; set; }
}
Controller:
public ActionResult Create()
{
//Populate DropDownList binding values
var model = new GroupViewModel
{
//Preselect the Lab with id 2
//LabId = 2,
Labs = repository.Labs.Select(c => new SelectListItem
{
Value = c.Id.ToString(),
Text = c.Name
}),
Terms = repository.Terms.Select(c => new SelectListItem
{
Value = c.Id.ToString(),
Text = c.Name
}),
Schedules = repository.Schedules.Select(c => new SelectListItem
{
Value = c.Id.ToString(),
Text = c.Name
})
};
return PartialView("_Create", model);
}
View:
#Html.DropDownListFor(m => m.LabId, new SelectList(Model.Labs, "Value", "Text"),
"Select", new { #class = "selectpicker" })
#Html.DropDownListFor(m => m.ScheduleId, new SelectList(Model.Schedules, "Value", "Text"),
"Select", new { #class = "selectpicker" })
#Html.DropDownListFor(m => m.TermId, new SelectList(Model.Terms, "Value", "Text"),
"Select", new { #class = "selectpicker" })
Hope this helps...