Html.dropdownlist does not display the default/selected value in the dropdown field

Question

I have a table with various rows and each row corresponds to an ID. For every row, I have EDIT option which when selected should enable the user to look at the default values corresponding to that ID in the 'Edit.chtml' fields and there by update it by erasing the default values and typing in the new entry and saving it.

In 'Edit.chtml', I have a field for "MANAGERS" that I need to populate with a dropdownlist of names with default/selected value displayed corresponding to the ID of the row where Edit operation is selected from the table. I am using viewBag but my problem is the dropdownlist is always displaying the first item in the list and not the selected value. Please see the code below.

Controller:
 //
        // GET: /ManagersNAMES/Edit/5

        public ActionResult Edit(int id)
        {
            using (var db = new InpEntities())
            {
                var list_managers = (from x in db.TABLE_MANAGERS
                                        select new TABLE_MANAGERSDTO
                                        {
                                            ID = x.ID,
                                            NAME = x.NAME,
                                        }).OrderBy(w => w.NAME).ToList();

                ViewBag.managers = new SelectList(list_managers, "ID", "NAME", id);

                return View();
            }
        }

        public class TABLE_MANAGERSDTO
        {
            public string NAME { get; set; }
            public int ID { get; set; }
        }

        //
        // POST: /ManagersNAMES/Edit/5

        [HttpPost]
        public ActionResult Edit(int id, TABLE_INSTITUTES dp)
        {
            try
            {

                using (var db = new InpEntities())
                {

                    TABLE_INSTITUTES tmp = (TABLE_INSTITUTES)db.TABLE_INSTITUTES.Where(f => f.ID == id).First();
                    tmp.MANAGER = dp.MANAGER;
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
            }
            catch
            {
                return View();
            }
        }

View: 'Edit.chtml'

@{
    ViewBag.Title = "Edit";
}

<h2>Edit</h2>
@using (Html.BeginForm())
{
    @Html.ValidationSummary(true)
    <fieldset>

    <div class="editor-label" style="font-weight:bold">MANAGER</div>
    <div class="editor-field">
        @Html.DropDownList("dp.MANAGER", (SelectList)ViewBag.managers)
    </div>

    <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

Answer 1

You need to set the selected id within the controller like this:

var list_managers =  list_managers.Select(x => new
                          {
                              Value = x.ID.ToString(),
                              Text = x.Name
                          })
                          .ToList();

ViewBag.managers = new SelectList(list_managers, "ID", "NAME", id);

And change your view to:

@Html.DropDownList("dpMANAGER", (SelectList)ViewBag.managers)

Answer 2

Just wrote @Html.DropDownList("dp.MANAGER", ViewBag.managers) without selectlist, becouse its already in type of SelectList.

And write ViewBag.managers = new SelectList(list_managers, "ID", "NAME"); like this