Regenerate Code-First database without adding any data

Question

In my code-first setup, I prefer not to allow the consumer (in this case a web-page) to be able to drop and recreate the database even at design time, for fear that I might forget to add appropriate logic later and shoot myself in the foot (to the effect of creating a database users with proper permissions before going live). Therefore this website has three projects associated with the solution:

Code First Project, which contains POCOs and initializers. There are two distinct ways of creating a DbContext instance, one that sets Database.SetInitializer to an initilizer that inherits from CreateDatabaseIfNotExists<MyContext> and the other way does with DropCreateDatabaseAlways<PanelisternaDbContext>. This ways I don't get any sneaky drop & recreates, and hopefully even if I somehow mess up the database user permissions later, the server side code wouldn't go mental and start deleting things.
Webpage Project, or generally any kind of consumer. The idea is that I create MyContext here which doesn't drop the database - ever.
Reset Project, which is a console app that actually does drop and recreate everything. It even asks me to type in some verification, so I don't run it by accident.

So, everything's great so far. Except I don't know how to actually drop and recreate the database without putting anything in it. I.e. the following code does what I want:

using (var myContext = MyDbContext.GetContext("connectionString", true)) 
//The trailing 'true' marks that the database is to be dropped and recreated.
{
    var user = new User {};
    myContext.Users.Add(user);
    myContext.SaveChanges();
    myContext.Users.Remove(user);
    myContext.SaveChanges();
}

As you can see, I'm adding and removing a User object so that SaveChanges() actually has something to do. If I just do a SaveChanges() the database would not drop/recreate.

So, without further ado, I'm looking for a cleaner method to achieve database recreation, and any comments or thoughts on this reset-based solution.

AlexWilson · Accepted Answer · 2011-08-11 00:39:32Z

8

In your console app, you could put the following:

Database.SetInitializer(new DropCreateDatabaseAlways<MyDbContext>());         
using (var myContext = MyDbContext.GetContext("connectionString")) 
{           
    context.Database.Initialize(force: true);      
}

This should force a drop and recreate, and you could use a custom initializer to create some initial data if required.

edited Aug 11, 2011 at 0:39

answered Aug 10, 2011 at 22:48

AlexWilson

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1 Comment

Gleno Over a year ago

Exactly what I was looking for, save for the setinitilizer bit, which i prefer to treat in the context class. Thanks!

Richard Forrest · Accepted Answer · 2011-08-08 14:32:05Z

2

When you initialise you DBContext you can check that the database exists and create it if it doesn't.

public MyDbContext(){
    Database.CreateIfNotExists();
}

answered Aug 8, 2011 at 14:32

Richard Forrest

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Comments

Vazgen Torosyan · Accepted Answer · 2016-04-22 11:43:17Z

There are four different database initialization strategies:

CreateDatabaseIfNotExists: This is default initializer. As the name suggests, it will create the database if none exists as per the configuration. However, if you change the model class and then run the application with this initializer, then it will throw an exception.

DropCreateDatabaseIfModelChanges: This initializer drops an existing database and creates a new database, if your model classes (entity classes) have been changed. So you don't have to worry about maintaining your database schema, when your model classes change.

DropCreateDatabaseAlways: As the name suggests, this initializer drops an existing database every time you run the application, irrespective of whether your model classes have changed or not. This will be useful, when you want fresh database, every time you run the application, like while you are developing the application.

You can also create your own custom initializer, if any of the above doesn't satisfy your requirements or you want to do some other process that initializes the database using the above initializer.

public class SchoolDBContext: DbContext { 
public SchoolDBContext(): base("SchoolDBConnectionString") 
{
    Database.SetInitializer<SchoolDBContext>(new CreateDatabaseIfNotExists<SchoolDBContext>());

    //Database.SetInitializer<SchoolDBContext>(new DropCreateDatabaseIfModelChanges<SchoolDBContext>());
    //Database.SetInitializer<SchoolDBContext>(new DropCreateDatabaseAlways<SchoolDBContext>());
    //Database.SetInitializer<SchoolDBContext>(new SchoolDBInitializer());
}
public DbSet<Student> Students { get; set; }
public DbSet<Standard> Standards { get; set; }
}

You can also create your custom DB initializer, by inheriting one of the initializers

public class SchoolDBInitializer :  CreateDatabaseIfNotExists<SchoolDBContext>{ 
   protected override void Seed(SchoolDBContext context)
    {   
       base.Seed(context);  
    }
}

Turn off DB Initializer in Code-First

You can also turn off the DB initializer of your application. Suppose, for the production environment, you don't want to lose existing data, then you can turn off the initializer, as shown in the following:

public class SchoolDBContext : DbContext
{   
   public SchoolDBContext(): base("SchoolDBConnectionString")
   {
      //Disable initializer
      Database.SetInitializer<SchoolDBContext>(null);
   }
   public DbSet<Student> Students { get; set; }
   public DbSet<Standard> Standards { get; set; }
}

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