Code first database migration

Question

We are using the Code-first approach without an Edmx file, its running fine to create database the first time.

But if I am adding new data entities say new class to my database context then it is not able to add that to new table in that database.

Say for example there are two table initially in database. ex Database : DbTest

Table : Tbl1, Tbl2

Now if I add new table, say class name 'Tbl3', then it should be adding it into the existing database.

Can any one please explain to me with an example how it can be achieved via code first approach?

I have seen mentioned something like Database.SetInitializer(new ........)

What do I need to put in the blank area of the constructor above?

Benjamin Gale · Accepted Answer · 2012-10-27 09:41:36Z

If you look in your database you will see a table called "EdmMetadata" which Entity Framework uses to determine if any changes have been made to your model since the database was created (which it has in your case).

The default behaviour is for an exception to be thrown if the model and database differ. To get different behaviour you will need to use an IDatabaseInitializer<TContext>.

Luckily, Entity Framework ships with some default implementations of this interface:

CreateDatabaseIfNotExists<TContext> - This will create the database if one doesn't already exist.
DropCreateDatabaseAlways<TContext> - This will re-create the database each time your application is run.
DropCreateDatabaseIfModelChanges<TContext> - This will re-create the database if a change is detected in the EdmMetadata table (usually as a result of creating new tables).

You can of course also create your own implementation of this interface by overriding the InitializeDatabase method.

an example of using one of these initialization strategies is shown below:

Database.SetInitializer(
    new DropCreateDatabaseIfModelChanges<NameOfYourDbContextClass>())

Think carefully before choosing an initialization strategy as you could end up losing data already entered into the database and this may not be what you want.

The implementations provided by Entity Framework provide a Seed method for loading your database with data so that you can preload your database with default data each time it is created.

This article provides further information.

Collectives™ on Stack Overflow

Code first database migration

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related