🚀 Entity Framework: Code First Approach in .NET

Entity Framework (EF) is a powerful Object-Relational Mapper (ORM) that allows developers to work with databases using C# classes instead of raw SQL queries.

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🔷 What is Entity Framework?

As discussed in the previous blog, Entity Framework simplifies database interaction by mapping C# objects to database tables, enabling clean, maintainable, and strongly typed data access.

+-------------------+       +---------------------+       +------------------+
|   C# Classes      | ----> | Entity Framework    | ----> |   Database       |
| (Entities)        |       | (ORM Layer)         |       | (Tables/Rows)    |
+-------------------+       +---------------------+       +------------------+

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🔷 Entities and Domain Classes

📌 Entity Classes

Entity classes represent database tables. Each object represents a row.

Example:

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
}

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📌 Domain Classes

Domain classes represent business logic and real-world concepts.

• Entities → have identity (Primary Key)
• Value Objects → no identity
• Aggregates → group of related entities

Example structure:

Domain Layer
   |
   |--- Student (Entity)
   |--- Address (Value Object)
   |--- Course (Aggregate Root)

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🔷 Entity Framework Approaches

Approach	Description	Use Case
Code First	Start with C# classes	New applications
Database First	Start with existing database	Legacy systems

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🚀 Hands-on: Code First Approach

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Step 1: Create C# Model Classes

Instead of creating a database first, we define models:

public class Student
{
    public int Id { get; set; }   // Primary Key
    public string Name { get; set; }
    public int Age { get; set; }
}

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Step 2: Create DbContext

using Microsoft.EntityFrameworkCore;

public class AppDbContext : DbContext
{
    public DbSet<Student> Students { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseMySql(
            "server=localhost;database=newdb;user=root;password=;",
            new MySqlServerVersion(new Version(8, 0, 0))
        );
    }
}

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Step 3: Install NuGet Packages

Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Tools
Pomelo.EntityFrameworkCore.MySql

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Step 4: Create Migration

Add-Migration InitialCreate

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Step 5: Create Database from Code

Update-Database

👉 This automatically generates:

• Database
• Tables
• Schema based on C# models

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📊 Code First Workflow Diagram

C# Entity Classes
       |
       v
DbContext + Migrations
       |
       v
EF Core Model Builder
       |
       v
Database Creation
       |
       v
Tables Generated Automatically

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🔧 CRUD Application Flow

User Input
   |
   v
Controller / Program.cs
   |
   v
DbContext
   |
   v
Entity Framework Core
   |
   v
Database (Insert / Update / Delete / Fetch)

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💻 Sample CRUD Code (Code First)

Git Repo: https://github.com/shoonyank/CodeFirstApproach

Insert Operation

using (var context = new AppDbContext())
{
    Student s = new Student
    {
        Name = "John",
        Age = 20
    };

    context.Students.Add(s);
    context.SaveChanges();
}

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Fetch Data

using (var context = new AppDbContext())
{
    var students = context.Students.ToList();

    foreach (var s in students)
    {
        Console.WriteLine(s.Name);
    }
}

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Update Data

using (var context = new AppDbContext())
{
    var student = context.Students.First();
    student.Name = "Updated Name";

    context.SaveChanges();
}

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Delete Data

using (var context = new AppDbContext())
{
    var student = context.Students.First();
    context.Students.Remove(student);

    context.SaveChanges();
}

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🎯 Key Learnings

• Understand ORM and Code First workflow
• Define database using C# classes
• Learn migration-based schema management
• Perform CRUD without writing SQL
• Build scalable backend applications

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📌 When to Use Code First?

✔ New applications
✔ Microservices architecture
✔ Agile development (frequent changes)
✔ Full control over schema design
✔ Domain-driven design (DDD)

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📎 Code First vs Database First (Quick Insight)

Feature	Code First	Database First
Starting point	C# classes	Existing DB
Schema control	Developer	Database
Flexibility	High	Limited
Best for	Modern apps	Legacy systems