Thursday, 21 February 2013

How to Seed/Initialise Some Data in Entity Framework Code First

Entity Framework version 5.0.0 is used when writing this post.

First, we need to create a class derived from one of the built in database initialiser options' classes. They are CreateDatabaseIfNotExists, DropCreateDatabaseIfModelChanges and DropCreateDatabaseAlways. In the example below is DropCreateDatabaseIfModelChanges. I think it is possible to create a custom initialiser if we wish to do so.
public class DBInitialiser : DropCreateDatabaseIfModelChanges<MyContext>
    protected override void Seed(MyContext context)
        // populate sizes table
        var sizes = new List<Size> {
            new Size {SizeId = 1, Code="S", Description="Small"},
            new Size {SizeId = 2, Code="M", Description="Medium"},
            new Size {SizeId = 3, Code="L", Description="Large"}
        sizes.ForEach(s => context.Sizes.Add(s));       
Notice that on line 1, we also pass the context type. Then we need to override the Seed() method and create some items to populate the database.

Next, we need to call Database.SetInitializer() method with an instance of the new derived class as its parameter when the application starts. In an MVC application, this would be inside Application_Start() in Global.asax.cs file.

If you have used Database.SetInitializer() with one of the built in database initialiser options as its parameter then you need to replace it with the new derived class' instance.
//Database.SetInitializer(new DropCreateDatabaseIfModelChanges<MyContext>());
    // Replaced the parameter with the new derived class' instance
    Database.SetInitializer<MyContext>(new DBInitialiser());

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