Object reference not set to an instance of an object. : The Official Microsoft ASP.NET Forums

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scarfey

Member

6 Points

Object reference not set to an instance of an object.

Nov 25, 2010 11:23 AM|LINK

Hi guys, I'm having a little trouble with creating an edit control method within my application. I have posted both the edit viewpage and controller for the edit method. It pulls the information from the database fine but when I go to edit anything and post it back it brings up the object reference error on line 18 of the edit page.

Any help would be greatly appreciated.

HOME CONTROLLER:

using UniApp.Controllers;
using System.Linq;
using System.Web.Mvc;
using System.Web.Mvc.Ajax;
using UniApp.Models;
using System;

namespace UniApp.Controllers
{
    public class HomeController : Controller
    {
        //
        // GET: /Home/

        private UniversityNewsEntities _db = new UniversityNewsEntities();

        public ActionResult Index()
        {
            var results = from t in _db.News
                          orderby t.posted descending
                          select t;

            return View(results);

        }

        //
        // GET: /Home/Details/5
        public ActionResult Details(int id)
        {
            var result = (from p in _db.News
                          where p.storyId == id
                          select p).FirstOrDefault();

            return View(result);
        }
        // GET /Home/ViewResults/

        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult Index(string header)
        {

            var search = (from q in _db.News
                          where q.headline.Contains(header)
                          orderby q.posted descending
                          select q);
            int count = search.Count();
            ViewData.Add("count", count);
            ViewData.Model = search;
            ViewData.Add("type", header);

            switch (count)
            {

                case 0:
                    ViewData["MessageCountString"] = "no messages";

                    break;

                case 1:

                    ViewData["MessageCountString"] = "one message";

                    break;

                default:

                    ViewData["MessageCountString"] = "messages : " + count;

                    break;

            }

            return View();
        }

        //
        // GET: /Home/Edit/5
        public ActionResult Edit(int id)
        {
            var productToEdit = (from p in _db.News
                                 where p.storyId == id
                                 select p).FirstOrDefault();
            return View(productToEdit);
        }
        //
        // POST: /Home/Edit/5
        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult Edit(News productToEdit)
        {
            try
            {
                var originalProduct = (from p in _db.News
                                       where p.storyId == productToEdit.storyId
                                       select p).FirstOrDefault();
                _db.ApplyPropertyChanges(originalProduct.EntityKey.EntitySetName,
                productToEdit);
                _db.SaveChanges();
                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }
    }
}

EDIT VIEWPAGE

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<UniApp.Models.News>"%>
<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
   Edit
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2>Edit</h2>

    <%= Html.ValidationSummary("Edit was unsuccessful. Please correct the errors and try again.") %>

    <% using (Html.BeginForm()) {%>

        <fieldset>
            <legend>Fields</legend>
            <p>
                <label for="posted">posted:</label>
                <%= Html.TextBox("posted", String.Format("{0:g}", Model.posted)) %>
                <%= Html.ValidationMessage("posted", "*") %>
            </p>
            <p>
                <label for="headline">headline:</label>
                <%= Html.TextBox("headline", Model.headline) %>
                <%= Html.ValidationMessage("headline", "*") %>

            </p>
            <p>
                <label for="story">story:</label>
                <%= Html.TextBox("story", Model.story) %>
                <%= Html.ValidationMessage("story", "*") %>
            </p>
            <p>
                <label for="image">image:</label>
                <%= Html.TextBox("image", Model.image) %>
                <%= Html.ValidationMessage("image", "*") %>
            </p>
            <p>
                <input type="submit" value="Save" />
            </p>
        </fieldset>

    <% } %>

    <div>
        <%=Html.ActionLink("Back to List", "Index") %>
    </div>

</asp:Content>

Reply

ignatandrei

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137682 Points

22147 Posts

Moderator

MVP

Re: Object reference not set to an instance of an object.

Nov 25, 2010 11:42 AM|LINK

scarfey
it brings up the object reference error on line 18 of the edit page.

What's the line 18 ?

anyway, please replace:

scarfey
var productToEdit = (from p in _db.News
                                 where p.storyId == id
                                 select p).FirstOrDefault();
            return View(productToEdit);

with

var productToEdit = (from p in _db.News
where p.storyId == id
select p).FirstOrDefault();

if(productToEdit == null)

return Content(" not found product with id = " + id);

else

return View(productToEdit)

My .NET blog : http://msprogrammer.serviciipeweb.ro/ |2012 Programmer tools

Reply

scarfey

Member

6 Points

26 Posts

Re: Object reference not set to an instance of an object.

Nov 25, 2010 12:00 PM|LINK

Hi,

Sorry I should of put what line 18 was, it's:

<%= Html.TextBox("posted", String.Format("{0:g}", Model.posted)) %>

Even when I commented it out it popped to the next textbox. I was thinking it might have something to do with the Model bit but i'm unsure.

Thanks for the speedy response

Jason

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ignatandrei

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Re: Object reference not set to an instance of an object.

Nov 25, 2010 12:37 PM|LINK

scarfey
Even when I commented it out it popped to the next textbox.

For sure. The " firstordefault" code means " give me null if you do not find anything in database"

Please try my code in controller action.

My .NET blog : http://msprogrammer.serviciipeweb.ro/ |2012 Programmer tools

Reply

scarfey

Member

6 Points

26 Posts

Re: Object reference not set to an instance of an object.

Nov 25, 2010 12:45 PM|LINK

I did try your code in my controller all star and it's still coming up with the same error. Like I said before it will pull the information from the database fine in order for me to edit. But once i go to submit anything that I have edited it brings back the error:

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

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

Source Error:

Line 16:             <p>
Line 17:                 <label for="posted">posted:</label>
Line 18:                 <%= Html.TextBox("posted", String.Format("{0:g}", Model.posted)) %>
Line 19:                 <%= Html.ValidationMessage("posted", "*") %>
Line 20:             </p>

Source File: c:\Users\Jason\Desktop\UniApp\UniApp\Views\Home\Edit.aspx Line: 18

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
   ASP.views_home_edit_aspx.__RenderContent2(HtmlTextWriter __w, Control parameterContainer) in c:\Users\Jason\Desktop\UniApp\UniApp\Views\Home\Edit.aspx:18
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +256
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.Control.Render(HtmlTextWriter writer) +10
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) in c:\Users\Jason\Desktop\UniApp\UniApp\Views\Shared\Site.Master:26
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +256
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.Control.Render(HtmlTextWriter writer) +10
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.Page.Render(HtmlTextWriter writer) +29
   System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) +59
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1266

Version Information: Microsoft .NET Framework Version:2.0.50727.4952; ASP.NET Version:2.0.50727.4955

Reply

ignatandrei

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137682 Points

22147 Posts

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MVP

Re: Object reference not set to an instance of an object.

Nov 25, 2010 01:37 PM|LINK

scarfey
I did try your code in my controller

Please list your action .

My .NET blog : http://msprogrammer.serviciipeweb.ro/ |2012 Programmer tools

Reply

scarfey

Member

6 Points

26 Posts

Re: Object reference not set to an instance of an object.

Nov 25, 2010 01:54 PM|LINK

Sorry i'm confused, my action?

I was wondering if it would be easier to try and throw all my existing code into a repository as the editing and creating looks to be a lot easier to figure out once it's in a repository.

Thanks for your help

Jason

Reply

ignatandrei

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137682 Points

22147 Posts

Moderator

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Re: Object reference not set to an instance of an object.

Nov 25, 2010 02:07 PM|LINK

scarfey
Sorry i'm confused, my action?

Yes, you have 3 action (index and details) where yuo are putting "firstordefault"

Both should handle for null

return Content(" not found product with id = " + id);

More, you have

catch
            {
                return View();
            }

please replace with

catch(Exception ex)
{

ModelState.AddModelError("",ex.Message);

return View(THEMODEL);
}

My .NET blog : http://msprogrammer.serviciipeweb.ro/ |2012 Programmer tools

Reply

sachingusain

Star

8786 Points

1702 Posts

Re: Object reference not set to an instance of an object.

Nov 25, 2010 02:43 PM|LINK

scarfey
   // POST: /Home/Edit/5
        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult Edit(News productToEdit)
        {
            try
            {
                var originalProduct = (from p in _db.News
                                       where p.storyId == productToEdit.storyId
                                       select p).FirstOrDefault();
                _db.ApplyPropertyChanges(originalProduct.EntityKey.EntitySetName,
                productToEdit);
                _db.SaveChanges();
                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }

Most likely in the above controller action, some exception is happening and it is going into the catch clause wherein you are returning "edit" view. That edit view is expecting some Model, but since you are not returning any (you are doing return View();) therefore you are getting object reference error.

You can put a breakpoint on catch clause and see for yourself.

You can replace it with return View(productToEdit); and it should work (this may not be the eventual solution). This will give you a hint where your controller and view are failing.

Please "Mark As Answered" if it helped you.

Thanks.

Reply

scarfey

Member

6 Points

26 Posts

Re: Object reference not set to an instance of an object.

Nov 25, 2010 03:49 PM|LINK

Hi sachingusain,

I tried the return view(productToEdit) and it's not giving the null object error but saying it within my edit page itself now.

After all this headache would it be better to try split my code into a repository because once ive got edited and create and delet I need to start getting it into some form of paging.

Thanks for all your help so far guys

Object reference not set to an instance of an object. RSS

19 replies

scarfey

Object reference not set to an instance of an object.

ignatandrei

Re: Object reference not set to an instance of an object.

scarfey

scarfey

scarfey

Re: Object reference not set to an instance of an object.

ignatandrei

Re: Object reference not set to an instance of an object.

scarfey

scarfey

Re: Object reference not set to an instance of an object.

Object reference not set to an instance of an object.

ignatandrei

Re: Object reference not set to an instance of an object.

scarfey

scarfey

Re: Object reference not set to an instance of an object.

ignatandrei

Re: Object reference not set to an instance of an object.

scarfey

sachingusain

Re: Object reference not set to an instance of an object.

scarfey

scarfey

Re: Object reference not set to an instance of an object.

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