Code First Migrations — Complete Guide

Code First Migrations — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of ASP.NET Core Tutorial on Toolliyo Academy.

8 min read Updated 6/25/2026

On this page

ASP.NET Core Tutorial (ShopNest) · Lesson 33 of 100

Code First Migrations

Beginner ✓ → Intermediate → Advanced → Professional

Intermediate · 2 — Building apps · ~14 min read · Module 4: Entity Framework Core

Introduction

You know the basics now. Here we use Code First Migrations in real app situations — controllers, databases, and APIs. Still plain language, just a bit more depth. Code First Migrations is part of reading and writing data with Entity Framework Core and SQL Server. Orders, products, and customers in ShopNest all persist through EF Core.

Database code causes many production bugs. Learn EF Core slowly — test queries in a small project first.

When will you use this?

Use EF Core when your app stores data in SQL Server, PostgreSQL, or SQLite.

Orders, customers, and products live in SQL Server — EF Core reads and writes them with C#.
Migrations let teams update database schema without manual SQL scripts in production.

Real-world: HDFC-style net banking API

The Banking team building HDFC-style net banking API uses Code First Migrations to add DiscountPercent column to Products without manual DBA scripts. account holders never see the C# code — they just get a fast, reliable transfer endpoints and account balance.

Production-style code

public class ShopDbContext : DbContext
{
    public ShopDbContext(DbContextOptions<ShopDbContext> options) : base(options) { }
    // DbSet properties for Code First Migrations
}

What happens in production: In HDFC-style net banking API, getting Code First Migrations right means account holders trust the transfer endpoints and account balance every day.

Lesson example (start here)

Copy this smaller example first. Once it works, compare it with the real-world code above.

public class ShopDbContext : DbContext
{
    public ShopDbContext(DbContextOptions<ShopDbContext> options) : base(options) { }
    // DbSet properties for Code First Migrations
}

Line-by-line walkthrough

Code	What it means
`public class ShopDbContext : DbContext`	DbContext — EF Core class that represents your database tables.
`{`	Part of the Code First Migrations example — read it together with the lines before and after.
`public ShopDbContext(DbContextOptions<ShopDbContext> options) : base(options) { }`	Method — often an action that runs when a URL is hit.
`// DbSet properties for Code First Migrations`	Comment — notes for humans; the compiler ignores it.
`}`	Closes a block started by { above.

How it works (big picture)

Study the example line by line.
Each part connects to Code First Migrations.
Edit one line, save, run dotnet run, and see what changes.

Do this on your computer

Update ShopDbContext or your entity classes.
Create or apply a migration if the schema changed.
Query or save data and verify in SSMS or Azure Data Studio.
Read the real-world section and name which part of the app uses this topic.
Run the example locally with dotnet run and confirm the same behavior.
Change one value in the example (route, text, or connection string) and predict what will happen before you save.

Experiments — try changing this

Change a string or route in the example and save — watch the browser or Swagger response update.
Break the code on purpose (remove a semicolon), read the error message, then fix it.
Add one more property to the entity class and create a migration.
Use dotnet watch run while editing Code First Migrations — the app restarts on save.

Remember

You learned what Code First Migrations is and when to use it in ShopNest. Practice by changing the example yourself. Use the Next link when you can explain it in your own words.

Common questions

What is Code First Migrations?

Code First Migrations is explained in the introduction above — read it in plain language first.

How long should I spend on Code First Migrations?

Until you can explain it in your own words and run the example without looking at the answer. Beginners often need 30–60 minutes per new concept; setup lessons may take one afternoon.

What if I get stuck on Code First Migrations?

Re-read the line-by-line walkthrough, check the terminal for red errors, and compare your code character-by-character with the example. Search the exact error text — someone else had it too.

Where is Code First Migrations used in real jobs?

See the real-world section above — the same pattern appears in LMS, banking, e-commerce, and SaaS backends. Interviewers ask you to explain it using one concrete example.