Question

I need some help with this error “The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.”

It’s a asp.net mvc3, EF4, and ms sql.
Here is the razor with two dropdowns:

<div class="editRow">
@Html.DropDownListFor(m=>m.IndustryId, (SelectList)ViewBag.Industry, @Empower.Resource.General.ddlDefaultVal, new { @class = "ddl400" })
@Html.ValidationMessageFor(m => m.IndustryId)
</div>
<div class="editRow">
@Html.DropDownListFor(m=>m.ProvinceId, (SelectList)ViewBag.Province, @Empower.Resource.General.ddlDefaultVal, new {@class = "ddl400"})
 @Html.ValidationMessageFor(m => m.ProvinceId)   
</div>

Controller:

 IndustryService indService = new IndustryService();
ViewBag.Industry = new SelectList(indService.GetAllIndustry(), "IndustryId", "IndustryName");
ProvinceService proService = new ProvinceService();
ViewBag.Province = new SelectList(proService.GetAllProvince(), "ProvinceId", "ProvinceName");
 return View();

ProvinceService:

public IEnumerable<Province> GetAllProvince()
        {
            using (var context = DBContext.ObjectContext)
            {
                var pros = context.Provinces;
                return pros;
            }
        }

IndustryService is identical as above…

public class DBContext
    {
        private static EmpowerDBEntities _empowerContext;
        public static EmpowerDBEntities ObjectContext
        {
            get
            {
                if (_empowerContext == null)
                    _empowerContext = new EmpowerDBEntities();
                return _empowerContext;
            }
        }
    }

I know the problem occurs in second dropdown when it tries to retrive data while the connection is desposed by previous query. Please help me with this, thanks.

Answer 1

The fix is simple – convert to a .ToList() or First() before using. LINQ has deferred execution and tries to run this command after the context is disposed (when your object results are referenced) – not when you actually make the call.. You need to force it to run now while the context is in scope.

using (var context = DBContext.ObjectContext)
{
     var pros = context.Provinces;
     return pros.ToList();
}

Also – your code above is checking for null in the get accessor. However this object won’t be null – it will be disposed, so you cannot do your check this way, you need to check if its null and not disposed.

public class DBContext
    {
        private static EmpowerDBEntities _empowerContext;
        public static EmpowerDBEntities ObjectContext
        {
            get
            {
                if (_empowerContext == null || _empowerContext.IsDisposed())
                    _empowerContext = new EmpowerDBEntities();
                return _empowerContext;
            }
        }
    }

something like that anyways 🙂