IT:AD:EF/CodeFirst/Migrations:HowTo:Add-Migration

(UP)

Summary

So…if Enabling Migrations and using IT:AD:EF/CodeFirst/Migrations:HowTo:Update-Database is too easy/dangerous, what's the safer approach?

The solution MS is pushing is to be more … careful.

Make changes to an Entity
Try to run
Get the exception that says the Model has changes
This time, instead of invoking IT:AD:EF/CodeFirst/Migrations:HowTo:Update-Database (with AutomaticMigrations=true), invoke:

     Add-Migration {MyUniqueName} -startupprojectname:App.AppHost.Web -projectname:App.Infrastructure -verbose -debug

This creates a new file in the Migrations folder, outlining the shape of the same entity, but with the added property.

Using a coded Migration file is referred to by MS as a Coded Migration.

Note:

File name has date prefix to provide processing order
Class that enherits from DbMigration

Note:
Given the limitations of automatic migrations we recommend using code-based migrations in team environments.
Src: MS: http://msdn.microsoft.com/en-US/data/jj554735

namespace XAct.Spikes.CodeMigration.Migrations
{
    using System;
    using System.Data.Entity.Migrations;
    
    public partial class AddEstimateDescription : DbMigration
    {
        public override void Up()
        {
            CreateTable(
                "dbo.Estimates",
                c => new
                    {
                        Id = c.Int(nullable: false, identity: true),
                        Name = c.String(nullable: false, maxLength: 50),
                        Amount = c.Double(nullable: false),
                        Description = c.String(),
                    })
                .PrimaryKey(t => t.Id);
            
        }
        
        public override void Down()
        {
            DropTable("dbo.Estimates");
        }
    }
}

Examples of the commands you have at your disposal to craft Migrations are: