Why is the Seed method called again in my EF code first migrations scenario? - ef-code-first

Question

I have a EF code first project and there is how I seed the database
internal sealed class Configuration : DbMigrationsConfiguration<myDB>
{
public Configuration()
{
AutomaticMigrationsEnabled = false;
ContextKey = "myDB.Auth.Service.DAL.myDB";
}
protected override void Seed(myDBdb)
{
var mProduct = new Product
{
Name = "default product",
CreatedDate = DateTime.Now
};
db.Products.AddOrUpdate(mProduct);
db.SaveChanges();
}
}
I have a wcf service that uses above code. What I realise is that every time I restart the wcf service (either from visual studio or IIS), above code is get called. As a result, multiple "default product" are added into the database, anyone knows why that happened?

Answer 1

Migration seed runs after every update-database so you need to make your script idempotent by testing for existance or using AddOrUpdate. If you only want to seed on database creation, there is a separate context seed method that only runs when the database is created.
https://blog.oneunicorn.com/2013/05/28/database-initializer-and-migrations-seed-methods/
AddOrUpdate for seeding
Edit:
When you use MigrateDatabaseToLatestVersion initializer, your seed method runs every time your application runs. If you want to control this process, switch your initializer to null:
Database.SetInitializer(new NullDatabaseInitializer<ApplicationDbContext>());
And then just manually run migrations when needed. To take it a step further, you can write your own initializer and do what you want when either the database does not exist or the database needs updating:
Database.SetInitializer(new ValidateDbInitializer<ApplicationDbContext>());
// ref: https://coding.abel.nu/2012/03/prevent-ef-migrations-from-creating-or-changing-the-database/
public class ValidateDbInitializer<TContext> : IDatabaseInitializer<TContext>
where TContext : ApplicationDbContext
{
public void InitializeDatabase(TContext context)
{
if (!context.Database.Exists())
{
throw new InvalidOperationException("The database does not exist. Check your server and connection string.");
}
if (!context.Database.CompatibleWithModel(true))
{
throw new InvalidOperationException("The database is not up to date. You may need to apply update(s).");
}
}
}

Answer 2

First step is to use the Tools menu, select Library Package Manager, then select Package Manager Console. In the Package Manager Console window type the below command.
Enable-Migrations
which will adds folder named as Migrations in your project and also a code file called as Configuration.cs.
in Configuration.cs type the below line
using yourprojectname.Models;
protected override void Seed(yourprojectname.Models.MyServiceContext context)
{
context.MyDB.AddOrUpdate(x => x.Id,
new MyData() { Name = "Mohit", CreatedDate= "14/05/2016" },
new MyData() { Name = "Prabhat", CreatedDate= "15/05/2016" },
);
}
Now type Update-Database
in Package Manager Console window

Answer 3

Try the following:
protected override void Seed(myDBdb)
{
var mProduct = new Product
{
Id = 1,
Name = "default product",
CreatedDate = DateTime.Now
};
db.Products.AddOrUpdate(mProduct);
db.SaveChanges();
}

Answer 4

When you are using the application for initialization the Data for the first time, please use DropCreateDatabaseAlways. e.g. :
public class MyClass : DropCreateDatabaseAlways<connectionstringContextName>
{
protected override void Seed(MyContext context)
{
// Your seed data
}
}