Entity Framework CodeFirst : Simple Migrations

Article
12/04/2013

When I change my model from let’s say

 //Employee Entity

public class Employee

    public int Id { get; set; }

    public string FullName { get; set; }

 //Employee Entity

public class Employee

    public int Id { get; set; }

    public string FullName { get; set; }

    public string Email { get; set; } //New

Then I find a trouble. Either I have to drop create the whole database using

 Database.SetInitializer<HRContext>(new DropCreateDatabaseIfModelChanges<HRContext>());

or I need to do it manually. But this deletes everything. Who wants that? No one. So I left with an option of reflecting only changes. Now in EF CodeFirst we call it as Migrations. This can be very in-depth customizable. I would like to show you the most simple option and you can take to complex user-defined approach based on your business need.

Step1: Run this command to your Package Manager Console

PM> Enable-Migrations

And the output would look like

After this two files will be created in project under a new folder “Migrations”

Then we need a small change there in the file configuration

 internal sealed class Configuration : DbMigrationsConfiguration<ConsoleApplication1.HRContext>

Would be changed to

 public sealed class Configuration : DbMigrationsConfiguration<ConsoleApplication1.HRContext>

And

 AutomaticMigrationsEnabled = false;

would change to

 AutomaticMigrationsEnabled = true;

Now the new Database initializer would look like,

 Database.SetInitializer<HRContext>(new MigrateDatabaseToLatestVersion<HRContext, Migrations.Configuration>());

So the complete code would look like

 public class Employee

    public int Id { get; set; }

    public string FullName { get; set; }

    public string Email { get; set; } //New

public class HRContext : DbContext

    public DbSet<Employee> Emps { get; set; }

class Program

    static void Main(string[] args)

        //Database.SetInitializer<HRContext>(new DropCreateDatabaseIfModelChanges<HRContext>());

        Database.SetInitializer<HRContext>(new MigrateDatabaseToLatestVersion<HRContext, Migrations.Configuration>());

        var emp = new Employee() { FullName = "Wriju Ghosh", Email = "some@contoso.com" };

        using (var ctx = new HRContext())

            //This would get me the database information

            string strConnection = ctx.Database.Connection.ConnectionString;

            Console.WriteLine(strConnection);

            ctx.Emps.Add(emp);

            ctx.SaveChanges();

            foreach (var em in ctx.Emps)

                Console.WriteLine(em.FullName);

                Console.WriteLine(em.Email==null?"null":em.Email);

Namoskar!!!

Share via

Entity Framework CodeFirst : Simple Migrations

Additional resources