ASP.NET身份工厂模式是否会破坏EntityFramework DbContext？

Question

This MSDN Blog Post recommends using the Factory Pattern to get, "an instance of UserManager per request for the application." Meanwhile, my web application is throwing an error saying it's problematic "if the same context instance is accessed by multiple threads concurrently." The blog seems to contradict the exception message. What gives?

The exception that I am receiving occurs on the following call:

IdentityResult result = await UserManager.CreateAsync(user, model.Password);

Larger blog context:

You can use Factory implementation to get an instance of UserManager from the OWIN context. This pattern is similar to what we use for getting AuthenticationManager from OWIN context for SignIn and SignOut. This is a recommended way of getting an instance of UserManager per request for the application.

Full exception text:

The context cannot be used while the model is being created. This exception may be thrown if the context is used inside the OnModelCreating method or if the same context instance is accessed by multiple threads concurrently. Note that instance members of DbContext and related classes are not guaranteed to be thread safe. "

Answer 1

The FactoryPattern does not break the DbContext; rather, it prevents the multiple thread problem.

UserManager.CreateAsync was throwing the exception because we had not properly implemented the factory pattern.

This following is correct. It creates a new instance of MyDbContext for each call to the UserManagerFactory function, and prevents multiple thread problems.

UserManagerFactory 
= () => new UserManager<IdentityUser>(new UserStore<IdentityUser>(new MyDbContext()));

The following is incorrect. It look similar to the above, but it does not create a new instance for each call to UserManagerFactory. It is what we were using, ergo we had one DbContext for the application, which meant sharing it with multiple threads concurrently, and blammo, exception.

var userStore = new UserStore<IdentityUser>(new MyDbContext());                    
var userManager = new UserManager<IdentityUser>(userStore);
UserManagerFactory = () => userManager;

Answer 2

I got that problem cause this:

IdentityResult result = await UserManager .CreateAsync(user, model.Password);

UserManager was a Property of the Authorization Filter Class and not called directly from the context in the function.

Correct : var userManager = context.Get<"ApplicationUserManager">()