DbContext has been disposed

Question

I developed a web application with ASP.NET MVC 4 and SQL Server 2008, I create ContextManager class to have only one database context in all pages.

public static class ContextManager
{
    public static HotelContext Current
    {
        get
        {
            var key = "Hotel_" + HttpContext.Current.GetHashCode().ToString("x")
                      + Thread.CurrentContext.ContextID.ToString();
            var context = HttpContext.Current.Items[key] as HotelContext;
            if (context == null)
            {
                context = new HotelContext();
                HttpContext.Current.Items[key] = context;
            }
            return context;
        }
    }
}

It works properly in most of the pages, but in registration page something goes wrong and my context gone deposed with following error:

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

public ActionResult Register ( RegisterModel model )
{
    if ( ModelState.IsValid )
    {
        // Attempt to register the user
        try
        {
            WebSecurity.CreateUserAndAccount( model.UserName, model.Password,
                                              new
                                               {
                                                      Email = model.Email,
                                                      IsActive = true,
                                                      Contact_Id = Contact.Unknown.Id
                                               } );

            //Add Contact for this User.
            var contact = new Contact { Firstname = model.FirstName, LastName = model.Lastname };
            _db.Contacts.Add( contact );
            var user = _db.Users.First( u => u.Username == model.UserName );
            user.Contact = contact;
            _db.SaveChanges();
            WebSecurity.Login( model.UserName, model.Password );

at the line _db.Contacts.Add( contact ); I got the exception.

But without using ContextManager by changing

HotelContext _db = ContextManager.Current;

into:

HotelContext _db = new HotelContext();

the problem was solved. But I need to use my own ContextManager. What is the problem?

Answer 1

Your context has been disposed somewhere else (not in the code you've shown), so basically when you access it from your Register action, it throws the exception.

Actually, you shouldn't use a static singleton to access to your context. Do instantiate a new DbContext instance for each request. See c# working with Entity Framework in a multi threaded server