The operation cannot be completed because the DbContext has been disposed using MVC 4

by

The problem you’re experiencing is due to LINQ’s deferred execution. It’s quite the gotcha for developers who haven’t yet realized how LINQ works under the hood. I have a great blog post about it, but the core concept is that you must force an enumeration on the collection to cause the LINQ code to run immediately instead of later. This means changing this:

model.PublisherList = context.Publishers.Select(x =>
    new SelectListItem()
    {
        Text = x.Name,
        Value = x.Id.ToString()
    });

to this:

model.PublisherList = context.Publishers.Select(x =>
    new SelectListItem()
    {
        Text = x.Name,
        Value = x.Id.ToString()
    }).ToList();

Note the .ToList() there which forces the enumeration.

Your LINQ query is deferred meaning that it is not being run at your controller but instead afterwards, probably in your view where you loop over the collection (which forces the enumeration and thus runs the LINQ). Because you’re using the using statement to dispose of your DB context (which is of course good practice), the context is disposed of before you reach the view, which executes the code against the disposed context. Forcing the enumeration within the using statement will run the code at that time, instead of later when the context is disposed, and prevent this issue.

More Related Contents:

  1. Filter/Search using Multiple Fields – ASP.NET MVC
  2. How to group by on 2 child entities and get total of both this child entities?
  3. LINQ to Entities does not recognize the method ‘System.Web.Mvc.FileResult’
  4. Export Model to DataTable
  5. Only primitive types or enumeration types are supported in this context
  6. One DbContext per web request… why?
  7. Why does the EF 6 tutorial use asynchronous calls?
  8. ‘Contains()’ workaround using Linq to Entities?
  9. Convert Linq expression “obj => obj.Prop” into “parent => parent.obj.Prop”
  10. How to add/update child entities when updating a parent entity in EF
  11. How to use a string to create a EF order by expression?
  12. How can I log the generated SQL from DbContext.SaveChanges() in my Program? [duplicate]
  13. LINQ to Entities only supports casting EDM primitive or enumeration types with IEntity interface
  14. Implementing Audit Log / Change History with MVC & Entity Framework
  15. Dynamic table name in linq [duplicate]
  16. Linq Syntax – Selecting multiple columns
  17. Configure multiple database Entity Framework 6
  18. Why is Asp.Net Identity IdentityDbContext a Black-Box?
  19. Join and Include in Entity Framework
  20. Creating dynamic queries with entity framework
  21. C# Entity-Framework: How can I combine a .Find and .Include on a Model Object?
  22. Log Queries executed by Entity Framework DbContext
  23. How to I apply filter while paginating in Asp.net MVC and entity Framework?
  24. Remove item from list based on condition
  25. Async PartialView causes “HttpServerUtility.Execute blocked…” exception
  26. How to group by DateTime.Date in EntityFramework
  27. Linq Query keeps throwing “Unable to create a constant value of type System.Object….”, Why?
  28. How to include() nested child entity in linq
  29. LINQ Query to Convert string to datetime
  30. Entity Framework select one of each group by date

Leave a Comment