How to call an Action from a helper and avoid the render?

Question

I'm working on ASP.NE MVC4 and I'm using LungoJS library for the development.

I'm developing a Helper to render LungoJS controls in the way I need.

For the Select inputs, I want to get a JSON that contains the data for each option.

I can get the needed JSON from an Action of a existing Controller.

But when I call the action from the helper, the view renders my html inside a <pre> tag :-(

View

    <div class="form" id="address-data">

        @Html.LungoInputFor(m => m.CaseServiceCaseModel.CaseAddressModel.AddressDataModel.TerritoryId, "text", @Labels.Territory, @htmlAttributesRO, true)
        @Html.LungoSelectFor(m => m.CaseServiceCaseModel.CaseAddressModel.AddressDataModel.TerritoryId, @Labels.Territory, null, true, "GetTerritoryKendo", "Address")

Helper

    public static MvcHtmlString LungoSelectFor<TModel, TValue>(this HtmlHelper<TModel> html, Expression<Func<TModel, TValue>> expression, string label = "", object htmlAttributes = null, bool fieldset = false, string action = "", string controller = "")
    {
        TagBuilder tag = new TagBuilder("select");
        JavaScriptSerializer js = new JavaScriptSerializer();

        MvcHtmlString data = ChildActionExtensions.Action(html, action, controller);
        object[] json = js.Deserialize<object[]>(data.ToString());

        foreach (Dictionary<string,object> item in json)
        {
            foreach (var property in item)
            {
                TagBuilder option = new TagBuilder("option");
                switch (property.Key)
                {
                    case "Selected":
                        if ((bool)property.Value)
                        {
                            option.MergeAttribute("selected","selected");
                        }
                        break;
                    case "Text":
                        option.InnerHtml = property.Value.ToString();
                        break;
                    case "Value":
                        option.MergeAttribute("value", property.Value.ToString());
                        break;
                    default:
                        break;
                }
                tag.InnerHtml += option.ToString(TagRenderMode.Normal);
            }
        }

        return MvcHtmlString.Create(tag.ToString(TagRenderMode.Normal));   
    }

I don't understand why if I'm getting the htmlstring from the Action in a variable, and after I return only the Select input html, affects the whole page... If I comment ChildActionExtensions.Action(html, action, controller) the view renders good (but without the content I need...)

Answer 1

You should not be using child actions here (ChildActionExtensions.Action helper) because they write directly to the response. What you could do instead is to include a property on your view model that will contain the collection you need and directly pass it as argument to your helper. Alternatively (but this is not a good solution) would be to call your DAL in the helper to retrieve the list.