How can I prevent EF "The context cannot be used while the model is being created" errors?

Looking at my Elmah error logs, I am seeing a few InvalidOperationExceptions from Entity Framework that deal with:

The context cannot be used while the model is being created.

This is with the latest EF CodeFirst library from Nuget. The only information I have been able to find on the net is that it is being caused by having data contexts as singletons, which is most certainly not my case. In my Windsor installer, my EF unit of work structure is being registered with:

container.Register(Component.For<IUnitOfWork>()
                            .ImplementedBy<EFUnitOfWork>()
                            .LifeStyle
                            .PerWebRequest);

I am able to recreate the error by hitting F5 in VS to start a 开发者_如何学编程debugging sessions, and while IIS is spinning up load up a second webpage to the debug session.

I suspect it is because the user is trying to access the system while Asp.net has unloaded due to the lack of activity, which makes sense as my product is currently in a very very small beta test. However, since real people are using the website with live data, I need as little errors occurring as possible.

Does anyone have any idea how to prevent this from occurring?

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Edit: I updated my windsor controller to now contain the following code:

        container.Register(Component.For<IUnitOfWork>().ImplementedBy<EFUnitOfWork>().LifeStyle.PerWebRequest);
        using (var context = new MyJobLeadsDbContext())
        {
            context.Set<UnitTestEntity>().Any();
        }

However, when I attempt to perform a 2nd web request while IIS is loading the application, the previous error still occurs

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Edit 2: As requested, here is the stack

   at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
   at System.Data.Entity.Internal.InternalContext.Initialize()
   at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)
   at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()
   at System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext()
   at System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider()
   at System.Linq.Queryable.Where[TSource](IQueryable`1 source, Expression`1 predicate)
   at MyApp.DomainModel.Queries.Users.UserByEmailQuery.Execute() in C:\Users\KallDrexx\Documents\Projects\MyApp\MyApp.DomainModel\Queries\Users\UserByEmailQuery.cs:line 44
   at MyApp.Infrastructure.MyAppMembershipProvider.GetUser(String email, Boolean userIsOnline) in C:\Users\KallDrexx\Documents\Projects\MyApp\MyApp\Infrastructure\MyAppMembershipProvider.cs:line 102
   at System.Web.Security.Membership.GetUser(String username, Boolean userIsOnline)
   at System.Web.Security.Membership.GetUser()
   at MyApp.MyAppBaseController.Initialize(RequestContext requestContext) in C:\Users\KallDrexx\Documents\Projects\MyApp\MyApp\MyAppBaseController.cs:line 23
   at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext)
   at System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext)
   at System.Web.Mvc.MvcHandler.<>c__DisplayClass6.<>c__DisplayClassb.<BeginProcessRequest>b__5()
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass1.<MakeVoidDelegate>b__0()
   at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.End()
   at System.Web.Mvc.MvcHandler.<>c__DisplayClasse.<EndProcessRequest>b__d()
   at System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f)
   at System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action)
   at System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult)
   at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

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I finally figured out the true cause of this, at least for me.

The issue was that I was retrieving a DbContext from Windsor in my custom Asp.Net Membership provider. This caused an issue because the membership provider has a lifespan of the whole application, while all other retrieval calls for the db context were new db contexts for the specific web requests. This meant that two database contexts were "spinning up" at the same time and thus this error was thrown.

This also caused a lot of hard to debug entity caching issues as well, so anyone who uses EF in their membership provider needs to be real careful about their context lifetime.

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Edit: In response to DotNetWise, I solved this by forcing my custom membership provider to always use an EF connection from Windsor by storing the Windsor connection factory in my constructor, then always retrieving my EF data context from the factory at that point.

For example:

public class CustomMembershipProvider : MembershipProvider
{
    private IServiceFactory _serviceFactory;

    public CustomMembershipProvider() : this(null) { }

    public CustomMembershipProvider(IServiceFactory factory)
    {
        // IF no factory was provided, we need to get one from the bootstrapper
        if (factory == null)
            _serviceFactory = new WindsorServiceFactory(Bootstrapper.WindsorContainer);
        else
            _serviceFactory = factory;
    }

    public override string ResetPassword(string email, string answer)
    {
        var unitOfWork = GetUnitOfWork();
        return new ResetUserPasswordCommand(unitOfWork).WithUserEmail(email).Execute();
    }

    private IUnitOfWork GetUnitOfWork()
    {
       return _serviceFactory.GetService<IUnitOfWork>();
    }
}

The idea being that any action the membership provider performs gets the UnitOfWork class from Windsor, and uses that to perform the action (in this case my UnitOfWork class is a repository holder to wrap up my EF data context)

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I ran into the same issue in a multithreaded WPF app.

My workaround was to force DbContext initialization from the Windsor installer:

container.Register(Component.For(TheDbContext.Blah.Blah));
using (var context = new TheDbContext())
      context.Set<SomeRandomEntity>().Any();

I might add in my opinion this qualifies as a bug in EF: they should have used thread-safe (with locks, or whatever) code for DbContext initialization.

Of course, a better solution is what NHibernate does: the SessionFactory is an explicitly created, separate object from the Session.

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When i encountered this issue, i found it was a dbconnection gone wrong.

I corrected my EntityFramework dbconnection string and all was fine