Entity Framework model change error

问题:

I am getting the error

"The model backing the 'DataContext' context has changed since the database was created. Consider using Code First Migrations to update the database".

I am using Entity Framework and have changed my model after declaring DataContext. How can I fix this error?

回答1:

1. If you already deployed your application or you don't want remove data from database you must read about Code First Migrations. Here you have a link: http://msdn.microsoft.com/en-us/library/hh770484(v=vs.103).aspx

2. If you can delete database just do it. EF will create new database that match your model.

3. You can also disable creating/updating database structure by invoking the following code:

   Database.SetInitializer<MyDbContext>(null);
   

回答2:

If you delete the __MigrationHistory table in SQL Server it should fix it.

回答3:

I used database first to create a project after I had changed my database context and solved my problem:

Database.SetInitializer<Models.YourDbContext>(null);

Don't forget to handle the DbUpdateException

回答4:

Delete the __MigrationHistory table in SQL Server or just or all rows of this table it should fix it