Q:

can't submit dropdownlistfor

My model :
    [Display(Name = "AO")]
    [Required]
    [StringLength(20)]
    public IEnumerable<SelectListItem> AO { get; set; }

My Controller:
public ActionResult ExpCreate()

 {
        List<SelectListItem> list = new List<SelectListItem>();
        list. Add(new SelectListItem { Text = "Pilih", Value = " " });
        var cat = (from c in db. AOs select c.UserID).ToArray();
        for (int i = 0; i < cat. Length; i++)
        {
            list. Add(new SelectListItem { Text = cat[i], Value = cat[i].ToString() });
        }
        ViewData["AODATA"] = list;
        ViewData["AODATAs"] = ViewData["AODATA"].ToString();
        return View();
    }

and my View :
Html. DropDownList("AO", (IEnumerable<SelectListItem>)ViewData["AODATA"])

then I got an error like this:
Unable to cast object of type 'System. Collections. Generic. List`1[System. Web. WebPages. Html. SelectListItem]' to type 'System. String'
What I must to do?  Please Help.  Thanks before

A:

Try changing the type of AO from IEnumerable<SelectListItem> to string. 
public string AO { get; set; }

Thanks!