Populate Dropdown in View from another Controller

Question

I am trying to populate a dropdown from another Controller. I have DeviceController that has a @Html.DropDownList that get populated. Originally I have the code that populates the DropDown in the controller. Now I am trying to move it to a Controller designated for dropdowns. So I have the code to populate the dropdown in one location instead of the same code in multiple Controllers. The dropdown loads correctly when I have it in the original controller however when I move it the DropDown controller I receive the following error There is no ViewData item of type 'IEnumerable<SelectListItem>' that has the key 'DropDownDeviceType'.

The code for my view -

  @Html.DropDownList("DropDownDeviceType", null, htmlAttributes: new { @class = "form-control" })

From my DropDownController (If I have this code in my DeviceController it works as intended)

public void PopulateDevciceType(object selectDeviceType = null)
    {
        string voidInd = "N";
        var deviceType = db.DeviceTypes
            .Where(x => x.VoidInd == voidInd)
            .OrderBy(x => x.DeviceType1);

        //ViewData["DropDownDeviceType"] = new SelectList(deviceType, "DeviceTypeID", "DeviceType1", selectDeviceType);
        ViewBag.DropDownDeviceType = new SelectList(deviceType, "DeviceTypeID", "DeviceType1", selectDeviceType);

    }

In my DeviceController

 //Populate dropdowns
    DropDownController dropDown = new DropDownController();
    dropDown.PopulateDevciceType(model.DeviceTypeID);

Answer 1

I understand your desire to farm out certain tasks to dedicated classes. However, I think you are overthinking this a little bit.

I'm not 100% sure what that error is actually telling you in terms of your code, but it seems like you've probably got some wonky view returns because your setting the ViewBag information within a different controller than the one that returns the view. Am I understanding that part of it correctly?

Instead of creating another controller class, create a static function somewhere that handles the list creations and ONLY the list creations. When it creates a list, have it return it.

Then, whenever you need a list to be populated, do this in the relevant controller method:

ViewBag.DropDownDeviceType= *wherever-your-static-method-is*.PopulateDeviceType(model.DeviceTypeID);