Bits of .NET

🗄️ Entity Framework = Data Access

SQL is tedious. Entity Framework is ORM. Query with C#, migrations, change tracking.

📝 EF Core Setup

# Install packages
dotnet add package Microsoft.EntityFrameworkCore
dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package Microsoft.EntityFrameworkCore.Design
dotnet add package Microsoft.EntityFrameworkCore.Tools

# Create DbContext
public class AppDbContext : DbContext
{
    public AppDbContext(DbContextOptions options)
        : base(options)
    { }
    
    public DbSet Users { get; set; }
    public DbSet Orders { get; set; }
}

# Models
public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public DateTime CreatedAt { get; set; }
    public List Orders { get; set; }
}

public class Order
{
    public int Id { get; set; }
    public int UserId { get; set; }
    public decimal Total { get; set; }
    public DateTime OrderDate { get; set; }
    public User User { get; set; }
}

# Register in Program.cs
builder.Services.AddDbContext(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

🎯 Querying with EF Core

public class UserService
{
    private readonly AppDbContext _context;
    
    public UserService(AppDbContext context)
    {
        _context = context;
    }
    
    public async Task GetUserByIdAsync(int id)
    {
        return await _context.Users
            .Include(u => u.Orders)
            .FirstOrDefaultAsync(u => u.Id == id);
    }
    
    public async Task> GetActiveUsersAsync()
    {
        return await _context.Users
            .Where(u => u.IsActive)
            .OrderBy(u => u.Name)
            .ToListAsync();
    }
    
    public async Task CreateUserAsync(User user)
    {
        _context.Users.Add(user);
        await _context.SaveChangesAsync();
        return user;
    }
    
    public async Task UpdateUserAsync(User user)
    {
        _context.Users.Update(user);
        await _context.SaveChangesAsync();
        return user;
    }
    
    public async Task DeleteUserAsync(int id)
    {
        var user = await _context.Users.FindAsync(id);
        if (user != null)
        {
            _context.Users.Remove(user);
            await _context.SaveChangesAsync();
        }
    }
}

💡 EF Core Tips

• Use async methods
• Include related data (Include/ThenInclude)
• Use AsNoTracking for read-only queries
• Manage migrations
• Use repository pattern for separation