public class Model
{
    public SelectList List{ get; set; }
}
public ActionResult Post()
{ 
   Model model = new Model();
   model.List = GetSelectList(id);
   return View(Model);
}

public SelectList GetSelectList(int selected)
		{
			var list = (from a in MyTable
						select new SelectListItem
						{
							Selected = a.ID == selected,
							Text = a.name,
							Value = a.ID.ToString(),
						}).ToList<SelectListItem>();

			list.Insert(0, new SelectListItem()
			{
				Text = "выберите один из элементов",
				Value = "-1"
			});

			SelectList sl = new SelectList(list, "Value", "Text", selected);
			return sl;
		}

@Html.DropDownList("id", (SelectList)Model.List, null)