The model backing the 'DataContext' contex

I am trying to use Code First with Migrations. Even though there are no current changes to my model, I'm getting an exception. When I add a migration, the up and down are empty, but I get a runtime error with the message as follows:

An exception of type 'System.InvalidOperationException' occurred in EntityFramework.dll but was not handled in user code

Additional information: The model backing the 'MyDataContext' context has changed since the database was created. Consider using Code First Migrations to update the database (http://go.microsoft.com/fwlink/?

My architecture is as follows:

DataAccess project that includes the context, fluid configurations and migrations code
Model project that contains the poco classes
Web API and MVC projects that each contain the connections string in their respective web.config files.

Additionally I have the following code:

DbInitializer

public static MyDataContext Create()
{
   Database.SetInitializer(new MigrateDatabaseToLatestVersion<MyDataAccess.MyDataContext, MyDataAccess.Migrations.Configuration>());
   return new MyDataContext(ConfigurationManager.ConnectionStrings["MyDataContext"].ConnectionString, null);
}

I started with AutomaticMigrationsEnabled = false; in the migration Configuration constructor, as it was my understanding that this would allow (and require) me to have more control over when migrations were applied. I have also tried setting this to true but with the same result.

I added a new migration upon receiving this error, and the Up method was empty. I updated the database to this new migration, and a record was created in the _migrationHistory table, but I still receive the error when I attempt to run the application. Also, the seed data was not added to the database.

protected override void Seed(MyDataAccess.MyDataContext context)
{
            IdentityResult ir;

            var appDbContext = new ApplicationDbContext();
            var roleManager = new RoleManager<IdentityRole>(new RoleStore<IdentityRole>(appDbContext));
            ir = roleManager.Create(new IdentityRole("Admin"));
            ir = roleManager.Create(new IdentityRole("Active"));
            ir = roleManager.Create(new IdentityRole("InActive"));

            var userNamager = new UserManager<User>(new UserStore<User>(appDbContext));

            //  assign default admin
            var admin = new User { UserName = "administrator", Email = "myAdmin@gmail.com" };
            ir = userNamager.Create(admin, "myp@55word");

            ir = userNamager.AddToRole(admin.Id, "Admin");
 }

where

public class ApplicationDbContext : IdentityDbContext<User>
{
    public ApplicationDbContext()
        : base("MyDataContext", throwIfV1Schema: false)
    {
    }
    ...

The question: If Add-Migration isn't seeing any change in the model, why do I get this error when I run? Why isn't the seed code being hit? How do I fix this, or if that can't be determined, how do I further determine the root cause?

回答1:

This worked for me.

Go to Package Manager Console and Run - Update-Database -force

回答2:

I am not sure if you found the answer to your problem, but this other answer I found here actually did it for me: Entity Framework model change error

I actually ended up deleting the __MigrationHistory table in SQL Server which I didn't know it was being created automatically.

The article also talks about the option to not generate it I think by using this instruction: Database.SetInitializer<MyDbContext>(null); but I have not used it, so I am not sure if it works like that

回答3:

I bet your data context is not hooking up the connection string. Check if it's not initialized with a localdb (something like (localdb)\v11.0) and not working with that when you might think it's set to something else.

回答4:

My issue ended up being a conflict between Automatic Migrations being enabled and the initializer MigrateDatabaseToLatestVersion as described here.