“There is no ViewData item of type 'IEnumerable<SelectListItem>'” error with custom model and list

Question

I have this dropdownlist in a view:

@Html.DropDownList("Sale.TypeTransaction", ViewBag.typetransaction as SelectList, new { @class = "form-control" })

As you can see, the name of the dropdownlist is Sale.TypeTransaction because Sale it's a model inside a custom model:

public class OfficeSale
{
    public OfficeSale()
    {
        SaleProductRelations = new List<SaleProductRelation>();
        Sale = new Sale();
    }
    public Sale Sale { get; set; }
    public List<SaleProductRelation> SaleProductRelations { get; set; }
}

Sale has the property TypeTransaction , it is a string . In my controller I fill the selectlist as follows:

    public ActionResult NewSale()
    {
        var list = new List<SelectListItem>();
        list.Add(new SelectListItem { Text = "Cash", Value = "Cash" });
        list.Add(new SelectListItem { Text = "Credit", Value = "Credit" });
        list.Add(new SelectListItem { Text = "Promotion", Value = "Promotion" });

        ViewBag.typetransaction = list;
        return View(new OfficeSale());
    }

I know if my viewbag has the same name of my property the dropdownlist is filled. But I cannot Write ViewBag.sale.typetransaction . Do you have any idea to solve this? Thanks in advance.

OK I tried the following as @StephenMuecke suggested and it worked:

    public ActionResult NewSale()
    {
        var list = new List<string>();
        list.Add("Cash");
        list.Add("Credit");
        list.Add("Promotion");

        ViewBag.typetransaction = new SelectList(list);
        return View(new OfficeSale());
    }

@Html.DropDownList("Sale.TypeTransaction", ViewBag.typetransaction as SelectList, new { @class = "form-control" })

Answer 1

ViewBag.typetransaction as SelectList this bothers me a lot.

As the DropDownList helper expects the second parameter to be an IEnumerable (I believe you are calling this constructor https://msdn.microsoft.com/en-us/library/dd470380%28v=vs.118%29.aspx ) you might need to cast to IEnumerable<SelectListItem> instead.

Answer 2

Your problem is that in the controller your assign ViewBag.typetransaction to typeof IEnumerable<SelectListItem> but then in the view you try and cast it to typeof SelectList which results in ViewBag.typetransaction being null .

SelectList is IEnumerable<SelectListItem> ( SelectList derives from MultiSelectList which derives from IEnumerable<SelectListItem> ) but IEnumerable<SelectListItem> is not SelectList

There a 2 options to solve this. First, in the view, cast the ViewBag property to the correct type in the html helper

@Html.DropDownList("Sale.TypeTransaction", ViewBag.typetransaction as IEnumerable<SelectListItem>, new { @class = "form-control" })

or alternatively, in the view, create a SelectList , for example

ViewBag.typetransaction = new SelectList(new List<string>() { "Cash", "Credit", "Promotion" });