c# - Why doesn't viewbag send data to view ?

I am new to MVC. I am using MVC 5.

I have created 2 controllers with GET and POST, namely AddStories.

What I want to do is that I post data and then return a list of data to view and then loop it over and display.

The 1st part such as posting data works perfectly but not the second part. It throws an error:

Object reference not set to an instance of an object.

Code:

Controller:

    [HttpGet]
    public ActionResult AddStories()
    {            
        return View();

    }

   [HttpPost]
    //[Bind("")]
    public ActionResult AddStories(Stories st, HttpPostedFileBase files)
    {

        try
        {
            basicoperations bo = new basicoperations();


            if (files != null)
            {
                string filePath = Path.Combine(Server.MapPath("~/UploadedFiles/"), Path.GetFileName(files.FileName));
                files.SaveAs(filePath);
            }

            st.Image = Path.GetFileName(files.FileName);



            if (bo.insertImages(st))
            {
                ViewBag.Data = "Added";

                List listofStories = new List();

                listofStories = bo.GetAllImages();

                ViewBag.Grid = listofStories;



            }
            else
            {
                return View("AddStories");
            }


        }
        catch (Exception ex)

        {
            ViewBag.Data = ex.Message;
        }

        return View("AddStories");
    }

View:

@model HimHer.Models.Stories



@using (Html.BeginForm("AddStories", "Stories", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    @Html.AntiForgeryToken()

    

        
Stories

        

        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        

            @Html.LabelFor(model => model.Story, htmlAttributes: new { @class = "control-label col-md-2" })
            

                @Html.EditorFor(model => model.Story, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Story, "", new { @class = "text-danger" })
            
        


        

            @Html.LabelFor(model => model.Image, htmlAttributes: new { @class = "control-label col-md-2" })
            

                
            
        

        

            

                

            
        
        





        
    
}




    @*
@ViewBag.Data
*@
    @{
        var listData = (List)ViewBag.Grid;
        if (listData.Count > 0)
        {
            foreach (var item in listData)
            {

                
item.Image
            }
        }
    }