Chaining multiple classes in a MVC4 view - asp.net-mvc

Question

Let's say I have a model like this (simplified from the original):
public class Location
{
public int ID { get; set; }
public string BinNumber { get; set; }
}
public class Item
{
public int ID { get; set; }
public string Description { get; set; }
public virtual Location Bin { get; set; }
}
public class LineOnPickList
{
public int ID { get; set; }
public virtual Item Item { get; set; }
}
The usual thing to do here on the LineOfPickList Create view would be to have a dropdownlist that listed all the Item Descriptions and put the selected item in the newly created LineOnPickList record when Create was clicked.
What I need to do however is show a dropdownlist of Location BinNumbers, yet still have the Item associated with that Location in the newly created LineOnPickList record.
How would that be done?

Answer 1

Define a view model for your drop down
public class ItemViewModel
{
public int ID { get; set; }
public string BinNumber { get; set; }
}
Then build the drop down list data in your controller action as follows
public class CreateLineOnPickListViewModel
{
public int ItemId { get; set; }
public IEnumerable<ItemViewModel> Items { get; set; }
}
public ActionResult Create()
{
var model = new CreateLineOnPickListViewModel();
model.Items = db.Items
.Select(i => new ItemViewModel { ID = i.ID, BinNumber = i.Bin.BinNumber });
return View(model);
}
Then in your view
#model CreateLineOnPickListViewModel
#Html.DropDownListFor(m => m.ItemId, new SelectList(Model.Items, "ID", "BinNumber"), "-")
Then your post action method in your controller would look like this
public ActionResult Create(CreateLineOnPickListViewModel model)
{
var item = new Item { ID = model.ItemID };
db.Items.Attach(item);
var lineOnPickList = new LineOnPickList { Item = item };
db.SaveChanges();
return View(model);
}