Question

I’m learning ASP.NET MVC. I had a small problem when dealing with dropdownlist.

This is what I did in controller

List<Int32> myList = new List<Int32>();
var a = (from m in datacontext.services
                 select m.ServiceID);
myList = a.ToList();
ViewData["ServiceID"] = new SelectList((IEnumerable<SelectListItem>)
                                a.ToList(), "ServiceID", "ServiceID");

In the view

 @Html.DropDownListFor(model => model.ServiceID, ViewData["ServiceID"] as SelectList)

This results in an error

Unable to cast object of type ‘System.Collections.Generic.List1[System.Int32]'
to type 'System.Collections.Generic.IEnumerable1[System.Web.Mvc.SelectListItem]’.”

How can this be resolved?

What’s the best way to deal with populating dropdownlist with a query?

Answer 1

There is an error in the cast.

To fix you can do this:

var a = datacontext.services.Select(arg => new { ServiceID = arg.ServiceID }).ToList();
ViewData["ServiceID"] = new SelectList(a, "ServiceID", "ServiceID");

or this:

var a = datacontext.services.Select(arg => arg.ServiceID).ToList();
ViewData["ServiceID"] = new SelectList(a);

In your code a is the list of integers. It cannot be cast into the list of SelectListItem.

Side note:
myList variable is not used in your code.