[Solved] ASP.Net MVC ViewBag foreach Error: Object reference not set to an instance of an object

chetan

SOLVED CLOSED ACTIVE ANSWERED
User: chetan
Posted: on Nov 08, 2020 10:33 PM
Forum: ASP.Net MVC
Answer: 1
Views: 17648
Sample Code: Download

I have the following MVC code:

getting the error in Ajax success foreach loop.

System.NullReferenceException: 'Object reference not set to an instance of an object.'

whole idea is on page load the list of products in dropdownlist.

on click of any product in dropdownlist,display the table or message saying that the offers available for the product is [offername].

        private CCIDataBaseEntities db = new CCIDataBaseEntities();
        // GET: Offers
        public ActionResult Index()
        {
            ViewBag.GetProduct = (from i in db.Table_Products
                                   select new
                                   {
                                       i.ID,
                                       i.ProductName
                                   }).ToList();
            return View();
        }

        public ActionResult Viewoffer(int productid)
        {
            try
            {
                if(productid != 0)
                {
                    var availableoffer = (from a in db.Table_DiscountOffers
                                          join b in db.Table_Products on
                                          a.Category equals b.Category
                                          where (a.IsActive == true) && (b.ID== productid)
                                          select new
                                          {
                                              offername=a.OfferName,
                                              productname=b.ProductName
                                          }).ToList();

                    if(availableoffer != null)
                    {
                        ViewBag.offers = availableoffer;
                    }

                }
                return new JsonResult
                {
                    Data = new { Success = true, ResultList = ViewBag.offers },
                    ContentEncoding = System.Text.Encoding.UTF8,
                    JsonRequestBehavior = JsonRequestBehavior.DenyGet
                };

            }
            catch(Exception ex)
            {
                return new JsonResult
                {
                    Data = new { ErrorMessage = ex.Message, Success = false },
                    ContentEncoding = System.Text.Encoding.UTF8,
                    JsonRequestBehavior = JsonRequestBehavior.DenyGet
                };
            }            
        }

View:

@model CCIApplication.ViewModal.ProductViewModel
@{
    ViewBag.Title = "View offers";
}

<h2>View offers</h2>
<div class="form-group">
    <div class="col-md-10">
        @Html.DropDownListFor(m => m.ProductName, new SelectList(ViewBag.GetProduct, "ID", "ProductName"), new { @onchange = "DropDownProductList();", @id = "productid" })
        @Html.ValidationMessageFor(model => model.ProductName, "", new { @class = "text-danger" })
    </div>
</div>
<script type="text/javascript">
    function DropDownProductList() {
        debugger;
        var array = @Html.Raw(Json.Encode(ViewBag.offers));
        var DropDownSelectedValue = $("[id*=productid]").val();
        $.ajax({
                    async: true,
                    type: 'GET',
                    dataType: 'JSON',
                    contentType: 'application/json;charset=utf-8',
                    data: { productid: DropDownSelectedValue },
                    url: '/Offers/Viewoffer',
                    success: function (Data) {

                        debugger;
                        if (Data.success == true) {
                            debugger;
                            alert(Data.ResultList)
                            alert(data.message);
                            @foreach(var student in ViewBag.offers)
                            {
                                <tr>
                                  <td>@student.offername</td>
                                  <td>@student.productname</td>
                                </tr>
                            }
                           // LoadRoomDetails();
                        }
                    },
                    error: function () {
                        alert("There is some issue.Error Occured");
                    }
                });
    }
</script>

what i am doing wrong over her?

on page load view throws nullreference exception.

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dharmend...

0 3

Reply
ANSWER
User: dharmendr
Replied: on Nov 09, 2020 03:03 AM
Report

Hi chetan,

Check this example. Now please take its reference and correct your code.

Model

public class ProductViewModel
{
    public string ProductName { get; set; }
}

Controller

public class HomeController : Controller
{
    // GET: Home
    public ActionResult Index()
    {
        var products = new[] {
            new { ID = 1, ProductName = "Chai" },
            new { ID = 2, ProductName = "Chang" },
            new { ID = 3, ProductName = "Aniseed Syrup" }
        }.ToList();


        ViewBag.GetProduct = products;
        return View();
    }

    public ActionResult Viewoffer(int productid)
    {
        try
        {
            if (productid != 0)
            {
                var availableoffers = new[] {
                    new { ID = 1, productname="Chai", offername="Offer 1" },
                    new { ID = 1, productname="Chai", offername="Offer 4" },
                    new { ID = 2, productname="Chang", offername="Offer 2" },
                    new { ID = 2, productname="Chang", offername="Offer 5" },
                    new { ID = 3, productname="Aniseed Syrup", offername="Offer 3" },
                    new { ID = 3, productname="Aniseed Syrup", offername="Offer 6" }
                };

                var availableoffer = availableoffers.Where(x => x.ID == productid).ToList();

                if (availableoffer != null)
                {
                    ViewBag.offers = availableoffer;
                }

            }
            return new JsonResult
            {
                Data = new { Success = true, ResultList = ViewBag.offers },
                ContentEncoding = System.Text.Encoding.UTF8,
                JsonRequestBehavior = JsonRequestBehavior.AllowGet
            };
        }
        catch (Exception ex)
        {
            return new JsonResult
            {
                Data = new { ErrorMessage = ex.Message, Success = false },
                ContentEncoding = System.Text.Encoding.UTF8,
                JsonRequestBehavior = JsonRequestBehavior.DenyGet
            };
        }
    }
}

View

@model Product_Offer_MVC.Models.ProductViewModel

@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Index</title>
</head>
<body>
    <h2>View offers</h2>
    <div class="form-group">
        <div class="col-md-10">
            @Html.DropDownListFor(m => m.ProductName, new SelectList(ViewBag.GetProduct, "ID", "ProductName"),
                                    "Select", new { @onchange = "DropDownProductList();", @id = "productid" })
        </div>
    </div>
    <h3>Available Offers</h3>
    <table id="tblOffers">
        <thead>
            <tr>
                <th>Offer Name</th>
                <th>Product Name</th>
            </tr>
        </thead>
        <tbody></tbody>
    </table>
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script type="text/javascript">
        function DropDownProductList() {
            var DropDownSelectedValue = $("[id*=productid]").val();
            $.ajax({
                async: true,
                type: 'GET',
                dataType: 'JSON',
                contentType: 'application/json;charset=utf-8',
                data: { productid: DropDownSelectedValue },
                url: '/Home/Viewoffer',
                success: function (Data) {
                    $('#tblOffers tbody').empty();
                    if (Data.Success == true) {
                        var html = "";
                        for (var i = 0; i < Data.ResultList.length; i++) {
                            html += "<tr><td>"+Data.ResultList[i].offername+"</td>";
                            html += "<td>"+Data.ResultList[i].productname+"</td></tr>";
                        }
                        $('#tblOffers tbody').append(html);
                    }
                },
                error: function (r) {
                    alert("There is some issue.Error Occured");
                }
            });
        }
    </script>
</body>
</html>

Screenshot

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[Solved] ASP.Net MVC ViewBag foreach Error: Object reference not set to an instance of an object

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