A Simple Step to Entity Framework: Code First Approach

Shiju Joseph
10y
55.3k
0
2

Article

Introduction

The Entity Framework is an Object Relational Mapping (ORM) providing an automated mechanism for CRUD operations to a database.

Entity Framework provides various approaches like:

Database first
Model First
Code First

This article explains the Code First approach. This is mainly used for domain driven development. Initially we are not focusing on the database development, so we are creating classes instead of tables in the database. Based on these classes we can simply create our database.

A quick start

1. Create a console application:

2. Add a new class:

3. Class name as Employee:

4. Write the field names in the Employee table (consider this Employee class is your Employee Table):

5. Go to the project References => Manage NuGet Packages.

6. Install EntityFramework:

7. Return to our Employee class and add the reference:

using System.ComponentModel.DataAnnotations;

ComponentModel.DataAnnotations

Provides attribute classes to define metadata for ASP.NET MVC and ASP.NET data controls.

System.ComponentModel.DataAnnotations Namespace.

Some examples

Table: Table Name
Column: Column name
Key: PK for the table
ForeignKey: FK Relation
Required: Required field validation
MinLength: Min length of the field
MaxLength: Max Length

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.ComponentModel.DataAnnotations;
namespace CodeFirstSampleAp
{
public class Employee
{
public Employee()
{
}
[Key]
public int EmpID { get; set; }
public string EmpName { get; set; }
public string Address { get; set; }
}
}

Add a new class MyContext and inherit the DbContext with a "using" for the reference as in the following:

using System.Data.Entity;

Next we need to plan about where we need to create our database. So in the app config create our connection string.

<connectionStrings>
<add name="MydbConn"
connectionString="Data Source=.;Initial Catalog=CompanyDB;Integrated Security=true"
providerName="System.Data.SqlClient"/>
</connectionStrings>

Then return to our MyContext class and pass our connection details here.

Also we can plan our database Initializer. That means all the time we don't want to create a new database. Based on our requirements we can plan this.

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace CodeFirstSampleAp
{
public class MyContext : DbContext
{
public MyContext()
: base("MydbConn")
{
Database.SetInitializer<MyContext>(new CreateDatabaseIfNotExists<MyContext>());
}
public DbSet<Employee> Employees { get; set; }
}
}

More options for the database Initializer:

Suppose we are working with a production db, so we can prevent or turn off this feature.

Database.SetInitializer<MyContext>(null);

Next go to main and add a value to our new table:

sing System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace CodeFirstSampleAp
{
public class Program
{
static void Main(string[] args)
{
MyContext context = new MyContext();
Employee emp = new Employee() { EmpID = 1, EmpName = "Shiju", Address = "Cochin" };
context.Employees.Add(emp);
context.SaveChanges();
}
}
}

Yes! Our Code First application is completed.

Go to our db. It automatically created the new db name CompanyDB that we specified in the AppConfig file.