Dropdown list in asp.net - asp.net

Question

i've a view. in the view i've months field(nvarchar type in database) :
#Html.DropDownListFor(model => model.rent_month,
(IEnumerable<SelectListItem>)ViewBag.months)
i've a method in a model class (PostManager) to generate months list like:
public IEnumerable<SelectListItem> GetMyMonthList()
{
return CultureInfo.CurrentCulture.DateTimeFormat.MonthNames
.Select(m => new SelectListItem() { Text = m, Value = m });
}
i get months in get action by :
public ActionResult Create()
{
PostModel p = new PostModel();
ViewBag.months = pm.GetMyMonthList();
return View(p);
}
in my Model my month attributes:
[Required(ErrorMessage = "You Must Select a Month.")]
[Display(Name = "Select Rent Month")]
public string rent_month { get; set; }
in the post action:
public ActionResult Create(PostModel p)
{
if (ModelState.IsValid)
{
post post = new Models.DB.post();
post.rent_month = p.rent_month;
db.posts.AddObject(post);
db.SaveChanges();
}
}
it generates month in the dropdownlist correctly.But after submit the form it gives error:
The ViewData item that has the key 'rent_month' is of type 'System.String' but must be of type 'IEnumerable'
now what is the solution for this error... thanks in advance...

Answer 1

I believe this is happening because in your post action you are not populating the ViewBag again. Make sure you set ViewBag.months = pm.GetMyMonthList(); in your controller POST action similar to what you have done in GET action.
Better solution would be to have a IEnumerable<SelectListItem> MonthList property as part of the PostModel. Instead of loading the months from ViewBag you can access it directly by the MonthList property
In the PostModel
public IEnumerable<SelectListItem> MonthList
{
get
{
return pm
.GetMonthList()
.Select(a => new SelectListItem
{
Value = a.Id,
Text = a.MonthText
})
.ToList();
}
}
Then in the view
#Html.DropDownListFor(model => model.rent_month, Model.MonthList)
After EDIT to the question
Your PostModel class should be like this. I have moved your GetMyMonthList() implementation out of the PostManager class.
public class PostModel
{
[Required(ErrorMessage = "You Must Select a Month.")]
[Display(Name = "Select Rent Month")]
public string rent_month { get; set; }
public IEnumerable<SelectListItem> MonthList
{
get
{
return CultureInfo.CurrentCulture.DateTimeFormat.MonthNames
.Select(m => new SelectListItem() { Text = m, Value = m });
}
}
}

Answer 2

public class PostModel
{
[Required(ErrorMessage = "You Must Select a Month.")]
[Display(Name = "Select Rent Month")]
public string rent_month { get; set; }
public IEnumerable<SelectListItem> MonthList
{
get
{
return CultureInfo.CurrentCulture.DateTimeFormat.MonthNames
.Select(m => new SelectListItem() { Text = m, Value = m });
}
}
}