• Enterprise quality ORM framework for .NET
• (Mostly) open source via Apache 2.0 license
  
• Originally released in 2008, current version: 6
• Database agnostic
• Largely convention based
  
• Distributed through NuGet

• LINQ to Entities (think: strongly typed SQL without the pain)
  
• Enterprise features: transactions, concurrency, logging, wide database support
  
• Async support
• Supports N-Tier architecture (self-tracking, DTO model)
• Migrations
• Code First workflow

//Automatically maps to dbo.Orders table

public class Order {
   public int Id      {get;set;}
   public string Name {get;set;}
   public virtual Customer Customer {get;set;}
   public virtual List<Product> Products {get;set;}
}

using (EFContext context = new EFContext())
{
  var orders = context.Orders.Where(o=> o.UserId == userId);
}  

List<Order> orders = new List<Order>();
using (SqlConnection connection = new SqlConnection("Server: 192.168..."))
{
  conn.Open();
  using (SqlCommand command = connection.CreateCommand()){
     command.CommandText = "sp_GetOrders";
     command.CommandType = CommandType.StoredProcedure;
     command.Parameters.AddWithValue("@UserID", userID);
     
     using(SqlDataReader = reader = command.ExecuteReader()){
       while(reader.Read()){
         Order newOrder = new Order();
         newOrder.ID = Convert.ToInt32(reader["Id"]);
         newOrder.Name = reader["Name"].ToString();
         orders.Add(newOrder);
       }
     }
  }
}

• Similar to Active Record
• Not enabled by default
• Supports "code first" migrations
• Does not export schema
• Supports seed data
• Supports scripting migration
• Doesn't play nicely with stored procedures

Enable-Migrations -EnableAutomaticMigrations
Add-Migration InitialCreate
Add-Migration AddOrderNotesColumn
Update Database

• Eager - think inner/left join
  
• Lazy - dynamically executed when accessed
• Explicit - null until explicitly loaded

• Model is defined  as POCOs vs dynamic at runtime
• "code first" migrations
• Active Record objects are CUD aware (i.e. person.save) whereas in EF you have DbContext
  
• Active Record classes inherit from ActiveRecord::Base whereas EF classes do not (need) to inherit from base class

• Testability (mocking DbContext not easy)
• Performance
• Separation of concerns (biz logic?)
• Produced SQL complex / inefficient sometimes
• Bloatware (1,000,000+ lines of code)

• Performance improvements
• Stored procedures for CUD
• Code based configuration enhancements
  
• Enum support
• Async queries built-in
• Testability improvements
• Query interception (logging, custom hooks ,etc.)
• Connection resilience