Using Entity Framework 6 (with code first approach), there is a exception if the database is not up to date
System.InvalidOperationException: "The model backing the 'xxx' context has changed since the database was created.
Is there a way to check, if the database is up to date and if not, update the database to the latest version from within the application itself?
Keeping your Database up to date with the EF Model is paramount.
For every change you make to the model of your context, there must be a migration to the database.
To maintain the integrity of the relationship between model and db you must:
Add-Migration migrationName_versionx.x.x
Update-Database
The exception you have experienced System.InvalidOperationException: is telling you that you that your model has not been migrated into your database. This means that EF is not able to work properly with possible queries you mave have.
Your database will keep a migration history which you can use to validate the integrity. If you are in doubt, simply apply a new migration and see if there were any changes.
This works using the DBMigrator Class
Dim migrator = New DbMigrator(new migrations.Configuration())
migrator.Update()
Related
Is there a way similar to Database.EncureCreated() method to ensure all migrations were executed from the app?
You can use Database.Migrate() - REF
From the article:
Applies any pending migrations for the context to the database. Will create the database if it does not already exist.
Note that Database.Migrate() is mutually exclusive with Database.EnsureCreated()
I am working with migrations in ASP .NET Core and Entity Framework and everything works well to preserve the structure of tables.
However, I would like (if possible) to also have data in migrations, so that a person who checkout my code (and migrations) can also retrieve that data (which would typically be test data or data that is stored in the database).
Is is possible? If not, what would be an alternative?
For example FluentMigrator allows that type of migration :
Insert.IntoTable("TestTable").Row(new { Name = "Test" });
In Entity Framework, migrations are used for creating Database Schema (not the data itself). If you need some type of data that should be included in the database while creating it, you should Seed the data while creating the schema.
If you want that one person to also retrieve your data then the connection string of that particular application should point to the same shared database where data actually resides.
is it possible to change database tables (e.g adding a field in a particular table) in an application using Entity framework.??
My application used an existing database to generate a model nd entity classes out of that database, if now I want to change tables in my existing database , how can I do that using Entity framework, so that:
Changes are saved in previously generated Entity classes
Changes are saved in database also.
Well you'll either have to change the database or the model classes.. If you don't want to update both manually, you could just update the database DDL and then generate the Entity model again.
In my code I am trying to check if my entity framework Code First model and Sql Azure database are in sync by using the "mycontext.Database.CompatibleWithModel(true)". However when there is an incompatibility this line falls over with the following exception.
"The model backing the 'MyContext' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data."
This seems to defeat the purpose of the check as the very check itself is falling over as a result of the incompatibility.
For various reasons I don't want to use the Database.SetInitializer approach.
Any suggestions?
Is this a particular Sql Azure problem?
Thanks
Martin
Please check out the ScottGu blog below:
http://weblogs.asp.net/scottgu/archive/2010/08/03/using-ef-code-first-with-an-existing-database.aspx
Here is what is going on and what to do about it:
When a model is first created, we run a DatabaseInitializer to do things like create the database if it's not there or add seed data. The default DatabaseInitializer tries to compare the database schema needed to use the model with a hash of the schema stored in an EdmMetadata table that is created with a database (when Code First is the one creating the database). Existing databases won’t have the EdmMetadata table and so won’t have the hash…and the implementation today will throw if that table is missing. We'll work on changing this behavior before we ship the fial version since it is the default. Until then, existing databases do not generally need any database initializer so it can be turned off for your context type by calling:
Database.SetInitializer<Production>(null);
Using above code you are no recreating the database instead using the existing one so I don't think using Database.SetInitializer is a concern unless you have some serious thoughts about using it.
More info: Entity Framework Code Only error: the model backing the context has changed since the database was created
Is it possible in any way to just update the database schema from entity model..? So that all the information in the database stays in the database? When you generate database from model the information will get lost.. I work against SQL Azure, and I have not found any tool to manage the tables and realations in the SQL Azure database in a proper way.. It would be soo nice if it could be done by the Entity Framework designer.
I think this will be resolved (from an entity framework point of view) in the next EF release.
From an azure point of view you can use SQL Azure Migration Wizard.