I'm using EF 4 and MVC in C#,
When my application loads, I would like load create some entities to be added to my database, so where is the best place to add thsi functionality using EF? Global.asax on Start application?
What is a reasonable name convention for the class... BootStrap?
Thanks
If you have existing database you should not include the initialization into your application. The only way how to make this work in existing database is to execute some initialization in Application_Start. The initialization must check existence of every entity you want to insert and insert data only if the entity is not present. Because your database already exists, the initialization logic will have to run every time you restart the application. To avoid this you would also need some flag in the database to mark that initialization was already done (one of inserted entity can be considered as a "flag" but only if the application cannot remove this entity).
EF normally seeds data only when creating database or after database migration.
Edit: If you are creating test data on your test database you should be happy with database recreation each time your model changes (or with migrations) and custom database initializer to seed your data.
Related
I am trying to develop my first Entity Framework code-first approach. I am little bit confused regarding Database.SetInitializer<> -
Can I set multiple initializer ? i.e.
Database.SetInitializer<Context>(new CreateDatabaseIfNotExists<Context>());
Database.SetInitializer<Context>(new DropCreateDatabaseIfModelChanges<Context>());
If I use only CreateDatabaseIfNotExists initializer, and later I change database server in connection string, then will the database be created on new server?
No you cannot set multiple initializer. Initializer Only insert data once in database after database created, and database creation script(internally) runs only when you will access any record of any table first time.
And before creating database EF always check first ,the database specified in connection string is present in database server. If database is not there then it will create.
The DropCreateDatabaseIfModelChanges initialisation strategy no longer works in MVC5 with ASP.NET identity.
I'm getting the following error:
The model backing the 'BaseModelContext' context has changed since the database was created. Consider using Code First Migrations to update the database.
What do I do if for now I don't want to use migrations? Shouldn't the fact that I've TOLD it to drop the database that it should then go and do it?
I'm using an existing database and I have mapped one of the tables as an entity (as i needed to map a foreign key).
So when it comes to initialising this database I would like EF to ignore this entity since it already exists.
How would I go about doing this?
You should create an empty migration as the first migration with the -IgnoreChanges flag to allow Entity Framework to get a snapshot of the existing database.
So out of the gate use:
Add-Migration InitialMigration -IgnoreChanges
and that will create a blank migration but it will update the Entity Framework metadata allowing the existing tables to exist and not be touched by migrations.
Also to be mentioned that the naming conventions that Entity Framework expects and your database schema may differ. You may need to manually setup the foreign keys using the Fluent API.
I didnt check with EF 6 specifically, but I think default EF behavious is that when the database exists, then it presume all model be ready and therefore will create no tables. If you want your initialization code to create tables with code first, use initialization code for prepare data. Look here :
http://www.entityframeworktutorial.net/code-first/seed-database-in-code-first.aspx
I am stuck trying to figure out how to set the database to run a migration on.
I have created a new empty project and set up Entity Framework using code first. I have all my classes built.
I want to add a new database and run the migrations on this. I have Migrations working but I can't figure out what database they are running on.
Is it possible to set the database you want to use for the migrations?
Multiple DBs for the same context gets a little tricky. But It is possible:
The essence of the problem is how EF decides which connection to use.
It will access instantiate the context without NO PARAMS during migration.
So depending on how that behaves influences you outcome and success.
Start here:
EntityFramework code-first custom connection string and migrations
I need to configure the database created by Entity Framework Code First MigrateDatabaseToLatestVersion class.
Is it possible to influence the database files parameters like size or maxsize? What interests me in particular, is there a way to add database files?
I assume I need to find the moment where the Entity Framework generates the CREATE DATABASE statement and influence it a bit. As far as I understand, the SqlServerMigrationSqlGenerator class is too late because the database already exists at this point.
Edit: According to comment this doesn't work:
You can just add code based migration using Add-Migration command and modify its Up method to execute Sql("ALTER DATABASE ...") and do what ever you want with your database.
Database is created through DbProviderServices - that is a bridging component between EF and specific database server. ObjectContext exposes operations for creating database and generating database creation script. DbMigrator use database creation operation when you execute Update. It checks that if Database exists and if not it uses ObjectContext.CreateDatabase. So if you want to change the process of creating the database you need to implement your own implementation of the migrator to change the way how Update method generates the database (maybe you just need a decorator which will create a database prior to executing DbMigrator.Update operation).