(IEnumerable)ViewBag.Name not working in ASP.Net

Question

i have a code below in my controller:

var getAllModel =
            VehicleManager.GetAllModelsByMakeId(getMakeId.MakeId)
                .Select(c => new SelectListItem {Text = c.Name, Value = c.ModelId.ToString()})
                .ToList();
var getAllTrim =
            VehicleManager.GetAllTrimByModelId(getModelId.ModelId)
                .Select(c => new SelectListItem {Text = c.Name, Value = c.TrimId.ToString()}).ToList();

ViewBag.ModelName = getAllModel;
ViewBag.TrimName= getAllTrim;

and in my .cshtml page also below:

var trimName = (IEnumerable<SelectListItem>)ViewBag.ModelName;
var modelName = (IEnumerable<SelectListItem>)ViewBag.TrimName;

Now i want to insert a trimName.Insert(0, new SelectListItem {Text= "Select", Value = ""}) but failed to access.

here's the problem i encountered: Object reference not set to an instance of an object. Anyone has a suggestion or explanation on this?

Unlike forum sites, we don't use "Thanks", or "Any help appreciated", or signatures on [so]. See "[Should 'Hi', 'thanks,' taglines, and salutations be removed from posts?](http://meta.stackexchange.com/questions/2950/should-hi-thanks-taglines-and-salutations-be-removed-from-posts). — John Saunders, Oct 17 '14 at 15:40
Sorry Guys, i solved the problem by changing the Class Bind to a certain List Before the declared problem. — Jed Monsanto, Oct 17 '14 at 17:53

score 0 · Answer 1 · edited May 23 '17 at 12:11

0

Use List<T> instead of IEnumerable<T> as IEnumerable<T> is sequential, From a SO answer:

The purpose of the IEnumerable interface is to allow a consumer to view the contents of a collection. Not to modify the values.

var trimName = (List<SelectListItem>)ViewBag.ModelName;
var modelName = (List<SelectListItem>)ViewBag.TrimName;

See this SO post to know why you cannot add item in IEnumerable<T>

edited May 23 '17 at 12:11

Community

1
1

answered Oct 17 '14 at 15:37

Ehsan Sajjad

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still the same problem – Jed Monsanto Oct 17 '14 at 15:40
@JedMonsanto but why do you want to append values to your data inside of the view. – meda Oct 17 '14 at 15:41
@JedMonsanto what is it you are trying to insert, do you need a default value, is that your goal ? – meda Oct 17 '14 at 15:46
make sure ViewBag.Model is not null it looks like it is coming null – Ehsan Sajjad Oct 17 '14 at 15:54
a Select word only... but beside, i cannot apply the insert in any of those variable like: trimName.Insert – Jed Monsanto Oct 17 '14 at 15:55
Sorry Guys, i solved the problem by changing the Class Bind to a certain List Before the declared problem. – Jed Monsanto Oct 17 '14 at 18:07

score 0 · Answer 2 · answered Oct 17 '14 at 16:11

If your only goal is to add an empty item to the select list, then there's a much easier way. Html.DropDownListFor takes a parameter to set up an empty item for you:

@Html.DropDownListFor(m => m.TrimName, (IEnumerable<SelectListItem>)ViewBag.TrimNameChoices, "Select an Option...")

Also, notice that I changed the name of your ViewBag variable. If your property on your model is TrimName you can't store your select list in ViewBag.TrimName or it will clobber any selected value. It's always better, if you're going to use ViewBag at all for select lists, to name them with something like Choices or Options at the end, so you don't have to worry about collisions like this.

Sorry Guys, i solved the problem by changing the Class Bind to a certain List Before the declared problem. — Jed Monsanto, Oct 17 '14 at 18:03

score 0 · Answer 3 · answered Oct 17 '14 at 16:31

0

Model

[Required]
[Display(Name = "Trim Name")]
public string TrimName{ get; set; }

Controller:

var getAllTrim =
            VehicleManager.GetAllTrimByModelId(getModelId.ModelId)
        .Select(c => new SelectListItem {Text = c.Name, Value = c.TrimId.ToString()})
        .ToList();

ViewBag.TrimList= getAllTrim;

View

@Html.DropDownListFor(model => model.TrimName, 
                  (IEnumerable<SelectListItem>)ViewBag.TrimList, "-- Select --")

answered Oct 17 '14 at 16:31

meda

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Sorry Guys, i solved the problem by changing the Class Bind to a certain List Before the declared problem – Jed Monsanto Oct 17 '14 at 17:55

(IEnumerable)ViewBag.Name not working in ASP.Net

3 Answers3