"The operation cannot be completed because the DbContext has been disposed"

Question

I am new at Entity Framework Code first and I am building a small app to get used to it.When the site runs for the first time I access existing catalog values inside the database and display this in a drop down using razor.

public void GetCats()
    {
        using (context = new RecipeContext())
        {
            try
            {
                var query = (from r in context.Catalogues
                             select r).Distinct().ToList();

                catalogues = query.Select(t => t.CatalogueName.ToString()).ToList();
                catalogues.Sort();


            }
            catch (Exception exe)
            {
                labMessage = exe.Message;

            }

        }
    }

Now when I try to add Catalogue values to the context I get the above error.

public void AddCatalogue(string catalogueName)
    {

        using(context = new RecipeContext())
        {
            try
            {
                catalogueName = catalogueName.ToLower();
                var catalogue = new RecipeCatalogue { CatalogueName = catalogueName };

                if (context.Catalogues.Where(t => t.CatalogueName == catalogueName).Count() > 0)
                {
                    labMessage = "The value already exists";
                    CatalogueNameAdded = false;
                    return;

                }
                context.Catalogues.Add(catalogue);
                context.SaveChanges();
                catalogueNameAdded = true;
                labMessage = "a new catalogue record was added";


            }
            catch (Exception exe)
            {
                catalogueNameAdded = false;
                labMessage = exe.Message;
            }

        }
    }

The values are being added to the database however but still get the above exception.

Advice perhaps as to why I get this error. This is my Controller method which calls the above method.

[HttpPost]
    public JsonResult AddNewCatalogue(string catalogueName)
    {
        ViewModel model = new ViewModel();
        model.AddCatalogue(catalogueName);
        return Json(new { ViewModel = model });

    }

Answer 1

Is context a field in your model? I think you shouldn't assign to a field in a using statement. At the closing brace of the using context will be disposed. If you access that field in another place (without re-assigning) you are accessing a disposed object that might raise the exception you are getting.

Try changing your using statetments like this using (var context = new RecipeContext()). (note var before context) and drop the field.

Answer 2

Your context is being disposed when the using block where you're performing your query is exited. That's the whole point of the using statement:

using(context = new RecipeContext()) {
    // ...
}
// context has been disposed at this point

Instead of a using statement, give your class a field to hold a reference to it.

private RecipeContext _context;

public void GetCats() {
    _context = new RecipeContext();
    // ...
}

public void AddCatalogue(string catalogueName) {
    // Use _context here
}

Just make sure that at some point, you call _context.Dispose(). Also, it's probably better to create the context in the constructor or someplace else that's only called once, prior to performing any operations with it.

Answer 3

Just my 2 cents:

The above answers are correct! If you're using some pattern like a repository, I sugest to implement it as a singleton! This way your objects will not be detached, and you're context will not be disposed!