EF Core Code First — Models, Migrations, Database

Introduction

Code First lets you design Hospital Management entities in C#, then generate and evolve the SQL Server schema with migrations — version control for your database.

After this article you will

• Create entities with conventions and annotations
• Run dotnet ef migrations add / database update
• Understand Up/Down migration methods
• Seed data with HasData and roll back migrations

Prerequisites

• Article 13 — EF Core Introduction
• ShopNest.Web project from prior lessons

Concept deep-dive

public class Patient
{
    public int Id { get; set; }
    [Required][MaxLength(120)]
    public string FullName { get; set; }
    public DateTime DateOfBirth { get; set; }
    public ICollection<Appointment> Appointments { get; set; }
}

// CLI
dotnet ef migrations add InitialHospitalSchema
dotnet ef database update

Migration Up() creates tables; Down() reverses. Never edit applied migrations in production — add new migration instead.

Hands-on — ShopNest Hospital Management

1. Entities: Patient, Doctor, Appointment.
2. Configure relationships in OnModelCreating (preview Fluent API Article 18).
3. Seed one doctor with HasData.
4. Inspect generated SQL in Migrations/*.cs.

Common errors & best practices

• Pending model changes — add new migration.
• Migration conflict on team — coordinate names; merge carefully.

Interview questions

Q: What does Update-Database do?
A: Applies pending migrations to the database in order.

Summary

• Migrations version schema changes
• Code First suits greenfield ShopNest modules
• HasData seeds reference data

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Next: EF Core CRUD Operations

FAQ