Работа с БД на CSharp — Шаг 2: Определение модели и контекста

using Microsoft.EntityFrameworkCore;

public class User
{
    public int Id { get; set; }
    public string Name { get; set; } = string.Empty;
    public string Email { get; set; } = string.Empty;
    public int Age { get; set; }
}

public class AppDbContext : DbContext
{
    public DbSet<User> Users { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseSqlite("Data Source=users_ef.db");
    }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<User>(entity =>
        {
            entity.HasIndex(u => u.Email).IsUnique();
        });
    }
}