Select Tag Helper: asp-for

Hello,

I'm constructing a view where I render the complete list of the classes grouped on a ViewModel. These are Stores and Departments (as cities).

I have a problem when I'm constructing the view, since the segment where I put the 'asp-action' tag helper.

This is my viewmodel called StoreIndexData:

public class StoreIndexData
{
public List Stores { get; set; }
public List Departments { get; set; }
}

This is my Index method where I initialize the models and send it to the view:

public async Task Index()
{
var viewModel = new StoreIndexData();
viewModel.Stores = await _context.Stores
.Include(c => c.StoreChains)
.Include(d => d.Districts)
.AsNoTracking().ToListAsync();
viewModel.Departments = new List();
viewModel.Departments = (from department in _context.Departments
select department).ToList();
viewModel.Departments.Insert(0, new Department { DepartmentID = 0, DepartmentName = "Select" });
ViewBag.ListofDepartment = viewModel.Departments;
return View(viewModel);
}

Then, in my view, I have this segment to show a dropdownlist for the department class:

="DepartmentName" class="control-label">
class="form-control"
asp-for="DepartmentID"
asp-items="@(new SelectList(ViewBag.ListofDepartment,"DepartmentID","DepartmentName"))">

When I debug the application, I get the following error:

'StoreIndexData' does not contain a definition for 'DepartmentName' and no extension method 'DepartmentName' accepting a first argument of type 'StoreIndexData' could be found (are you missing a using directive or an assembly reference?)
1. #pragma warning restore 1998
'StoreIndexData' does not contain a definition for 'DepartmentID' and no extension method 'DepartmentID' accepting a first argument of type 'StoreIndexData' could be found (are you missing a using directive or an assembly reference?)
1. #pragma warning restore 1998

So, which would be the correct way to use the tag helpers in this case?

I tried to debug the application deleting the asp-for tag helper and it runs as expected, but I don't believe this is the right thing to do. Any explanation on why is it important to use this tag helper?

Thanks!

_EDIT:

Ok, so first, since I'm using a ViewModel, I would need to access the model that contains this property, which is Department, like this:

for="Departments.DepartmentName" class="control-label">

BUT, I don't have a singular Department, so, If i changed the ViewModel like this:

public class StoreIndexData
{
public List Stores { get; set; }
public List Departments { get; set; }
public string DepartmentName { get; set; }
public int DepartmentID { get; set; }
}

and change the view back to this:

for="DepartmentName" class="control-label">
class="form-control"
asp-for="DepartmentID"
asp-items="@(new SelectList(ViewBag.ListofDepartment,"DepartmentID","DepartmentName"))">

It works, but I'm not sure if this is the correct procedure.

Select Tag Helper: asp-for

'StoreIndexData' does not contain a definition for 'DepartmentName' and no extension method 'DepartmentName' accepting a first argument of type 'StoreIndexData' could be found (are you missing a using directive or an assembly reference?)

'StoreIndexData' does not contain a definition for 'DepartmentID' and no extension method 'DepartmentID' accepting a first argument of type 'StoreIndexData' could be found (are you missing a using directive or an assembly reference?)