Entity Framework Code-First Migrations

Creating the Project

1. Create MVC project with Web API template
2. Create context class that inherits from DbContext

   
   									public class ServicesContext : DbContext
   								

Enabling Code-First Migrations

1. Enable migrations from the Package-Manager console

   
   									PM> Enable-Migrations
   								

2. Allow Code-First migrations in the generated Configuration.cs

   
   									public Configuration() 
   {
       AutomaticMigrationsEnabled = true;
   }
   								

Build Models

1. Create basic C# objects
2. Any references to other objects should simply be that type, NOT an int ID type.
   Good:

   
   									public Contact ServiceAgentContact { get; set; }
   								

   Bad:

   
   									public int ServiceAgentContactId { get; set; }
   								

Migrating

1. Add entities to DbContext to be picked up on migration

   
   									public DbSet<Contact> Contacts { get; set; }
   								

2. Update from Package-Manager console

   
   									PM> Update-Database
   								

Basics Notes and Gotchas

• References to other models default to many-to-one, and optional
• Primitives default to non-nullable, as well. Use Nullable version to fix

  
  ...									
  public int? OptionalValue { get; set; }
  public DateTime? OptionalDate { get; set; }
  ...
  								

Configuring

Use Attributes to enhance relationships

...
//Make Partner required for this model.
[Required]
public Partner Partner { get; set; }
public string CompanyName { get; set; }
...
							

Advanced

Modify relationships during migration run using Fluent API

public class ServicesContext : DbContext
{
	protected override void OnModelCreating(DbModelBuilder modelBuilder)
	{
	    modelBuilder.Entity<Partner>()
	        .HasOptional(p => p.Logo)
	        .WithOptionalDependent()
	        .Map(k => k.MapKey("Logo_Id"));
	    ...
	}
}
						

Will set Partner.Logo to be 1:1, but still optional