Sorry, an error occurred while processing your request. in MVC3 Model Entities [duplicate]

This question already has answers here: What is a NullReferenceException, and how do I fix it? (27 answers) Closed 4 years ago.

I am new in MVC, made an app that works on my local machine (Windows 7 with SQLExpress) but when I deploy live on Windows 2008 R2, SQL 2008 R2 and IIS7, I get this error: "Sorry, an error occurred while processing your request"

Below are snippets of the code in question:

WEB.CONFIG connectionStrings

add name="RentalEntities" connectionString="Data Source=[ServerName];Initial Catalog=[DatabaseName];Integrated Security=True" providerName="System.Data.SqlClient" 

HOMECONTROLLER

namespace Rental.Controllers    
{    
   RentalEntities rentalDB = new RentalEntities();

   ...

   public ActionResult Index()

   {             
      var listings = from l in rentalDB.Listings select l;
      return View(listings.ToList());    
   }
}

HOME/INDEX.CSHTML

@model List<Rental.Mode开发者_运维知识库ls.Listing>

@foreach (var listing in Model)    
{    
    @listing.ListingName <br />     
}

The error occurred on this line @foreach (var listing in Model), something to do with being null - note that NONE of the fields in the database are null. Any help will be appreciated.

---

Below is the full error message: [ where line 13 is: foreach (var listing in Model)

Sorry, an error occurred while processing your request.

System.NullReferenceException: Object reference not set to an instance of an object. at ASP._Page_Views_Home_Index_cshtml.Execute() in c:\inetpub\wwwroot\projects\Rentals\Views\Home\Index.cshtml:line 13 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.StartPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName)

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What has happened here is that you've passed a null value into the Model for index.cshtml. The code is foreach'ing over null.

Debugging this in Prod:

• How many rows are in the Listing table on the Prod server?
• Does your LINQ To SQL .dbml refer exactly to the connection string in your web.config, or does it have a hidden connection string buried within the .designer.cs?

• Try setting up some debug info on INDEX.CSHTML

  @(Model==null) //will write to page whether the model data being passed is null.
  

Debugging this in Dev/Test:

• To help debug why it's null, set a breakpoint for yourself on the line in Index(). Set it on return View(listings.ToList());. Is it actually null? Then set a breakpoint on the check for null in your View.

Before foreach, run a check for null:

@if (Model != null)
{
     foreach (var foo in Model)
     {
       //your code
     }
}
else
{
    @: Model Is null!
}