Working with Entity framework (Code First)

Entity Framework is the ORM that has been pushed by the MSFT giant over the last few years to the .NET community.

Working with Entity Framework

Entity framework comes in two flavors Code First and Database First

Code first is MSFT's way of using Entity Framework to scaffold your database from code. This huge feature allows you, the developer, to not write any SQL to create the database.

Database Philosophy

MSFT's tutorials with EF really push you toward having Entity Framework create the database, and use some Linq tricks to generate all the SQL. Now one of the huge downsites to this philosophy is that there is no stored procedures you can magically change to fix any database performance issues. This means any changes to alter the way you query should be done with a new deployment of the application. This also means that you will not have the oppertunity to profile any sprocs, and try to gain CPU cycles in the database. If you are looking for high performance I would look toward using Dapper instead. The benefit for using EF, is honestly developer time. You can get started much faster using Entity Framework's code first approach.

Getting Started with Code First

To put it simply make a class(or classes) and make a context which contains a set of those classes. Make sure you first add the entity framework nuget package.

    public class Employee
    {
        [Key]
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }

    }
    public class SomethingElse
    {
        [Key]
        public int Id { get; set; }
        public string Yup { get; set; }
        public string ImCool { get; set; }

    }
    public class ApplicationDbContext : DbContext
    {
        public ApplicationDbContext()
            : base("DefaultConnection")
        {
        }
        public DbSet<Employee> EmployeesetSet { get; set; }
        public DbSet<SomethingElse> SomethingElseSet { get; set; }


    }

then in the package console window type enable-migrations this will create a migrations folder and a configuration. If you wish your code to auto create the database on start, then add AutomaticMigrationsEnabled = true; to the Configurations.cs file that is created.

Then simply type add-migration give it a name, and the migration will look something like the following.

    public partial class one : DbMigration
    {
        public override void Up()
        {
            CreateTable(
                "dbo.Employees",
                c => new
                    {
                        Id = c.Int(nullable: false, identity: true),
                        FirstName = c.String(),
                        LastName = c.String(),
                    })
                .PrimaryKey(t => t.Id);

            CreateTable(
                "dbo.SomethingElses",
                c => new
                    {
                        Id = c.Int(nullable: false, identity: true),
                        Yup = c.String(),
                        ImCool = c.String(),
                    })
                .PrimaryKey(t => t.Id);

        }

        public override void Down()
        {
            DropTable("dbo.SomethingElses");
            DropTable("dbo.Employees");
        }
    }

You can then type update-database, and it will update the database. Note: the connection string is defined in the web config, and is declared on the following line.

YourDbContext.cs

public ApplicationDbContext() : base("DefaultConnection")

Web.config:

< connectionStrings>
    < add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\aspnet-WebApplication11-20141116030948.mdf;Initial Catalog=aspnet-WebApplication11-20141116030948;Integrated Security=True"
      providerName="System.Data.SqlClient" />
  </ connectionStrings>

See we have a connectionstring in our webconfig called DefaultConnection, and using our base constructor we are naming that as our connection.