@using SchoolIn.Models

if (Model.Enrollments != null)
        {
            @Html.DropDownList("searchString", Model.Enrollments.FirstOrDefault().weekDays.Select(s => new SelectListItem { Text = s.ToString(), Value = s.ToString() }))
        }

public virtual string classDays { get; set; }
 public string[] weekDays = new string[6]          { "Day", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday" };
 public string[] WeekDays
 {
 get { return weekDays; }

@{
    var Items = Model.Enrollments.FirstOrDefault().weekDays.Select(s =>
        new SelectListItem { Text = s.ToString(), Value = s.ToString()
            Selected = s.ToString().Equals(PreviouslySelectedValue)
        }
    );
}
@Html.DropDownList("searchString", Items)

@Html.DropDownListFor(model => PreviouslySelectedValue, Items)

public static MvcHtmlString DropDownListFor<TModel, TProperty>(
    this HtmlHelper<TModel> htmlHelper,
    Expression<Func<TModel, TProperty>> expression,
    IEnumerable<SelectListItem> selectList
)

public static IEnumerable<SelectListItem> SetSelected(this IEnumerable<SelectListItem> selectList, object selectedValue)
{
    selectList = selectList ?? new List<SelectListItem>();
    if (selectedValue == null)
        return selectList;
    var vlaue = selectedValue.ToString();
    return selectList.BuildList(m => m.Text, m => m.Value, null, m => String.Equals(m.Value, vlaue, StringComparison.CurrentCultureIgnoreCase));
}

@Html.DropDownListFor(model => model.CategoryId, ((IEnumerable<SelectListItem>)ViewData["Categories"]).SetSelected(model.CategoryId))