ASP.NET/02_ProjectOrientedSessions/Session02/Session 02 Document.md

1. Configurations

Preparation

• Read the documentation: https://learn.microsoft.com/en-us/ef/core/modeling/

Branching

• Create the feature/entity-configurations branch based on develop

Where Should You Place Configuration Files?

✅ Best Practice: Place all configuration files in the Infrastructure layer.
📂 Suggested Folder: Infrastructure/Configurations

Reason:

• The Domain layer should be clean (only entities, no database-related logic).
• The Infrastructure layer handles database interactions, so configurations belong here.

Create configuration classes

• Create the classes with this format: [Entity]Configutaion.cs
• The class should implement the IEntityTypeConfiguration<[Entity]>

Examples and Details

Use this as a reference:

https://github.com/MehrdadShirvani/AlibabaClone-Backend/tree/develop/AlibabaClone.Infrastructure/Configurations

How to Define Keys (Primary Keys & Identity)

You don’t need to explicitly define the primary key (PK) if you follow EF Core conventions (Id or EntityNameId). However, if you want to be explicit:

public class TicketConfiguration : IEntityTypeConfiguration<Ticket>
{
    public void Configure(EntityTypeBuilder<Ticket> builder)
    {
        builder.HasKey(t => t.Id); // Explicitly defining PK (optional)

        builder.Property(t => t.Id)
               .ValueGeneratedOnAdd(); // Sets Identity (auto-increment)
    }
}

🛑 NOTE: If you’re using a GUID as the ID, you might need .ValueGeneratedNever() instead.

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How to Define Foreign Keys?

Use HasOne() and WithMany() for one-to-many relationships.

public class TicketConfiguration : IEntityTypeConfiguration<Ticket>
{
    public void Configure(EntityTypeBuilder<Ticket> builder)
    {
        builder.HasKey(t => t.Id);

        // Foreign Key - Ticket to Transportation
        builder.HasOne(t => t.Transportation) 
               .WithMany(tr => tr.Tickets)   
               .HasForeignKey(t => t.TransportationId)
               .OnDelete(DeleteBehavior.Restrict); // Optional: No cascade delete
    }
}

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How to Introduce Navigation Properties with Different Names?

If your navigation property doesn’t match the entity name, you should explicitly specify it using HasOne() and WithMany().

Example: Ticket has a Buyer (which is an Account)

builder.HasOne(t => t.Buyer)  // Navigation property (Ticket → Account)
       .WithMany(a => a.TicketsBought) // Corresponding collection in Account
       .HasForeignKey(t => t.BuyerId);

Tip: If your navigation property names don't match table names, always define them explicitly in the Fluent API.

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How to Configure Column Types? (nvarchar, date, etc.)

You can manually specify column types using .HasColumnType().

All Strings Should Be nvarchar with Specific Lengths

builder.Property(t => t.TicketNumber)
       .IsRequired()
       .HasMaxLength(20) // Limits nvarchar length
       .HasColumnType("nvarchar(20)");

Store Some DateTime Fields as SQL DATE Instead of DATETIME2

builder.Property(t => t.PurchaseDate)
       .HasColumnType("date");  // Instead of default "datetime2"

🚀 Best Practice: Always set string lengths to avoid nvarchar(MAX), which hurts performance.

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How to Define Constraints? (Not Null, Length, etc.)

Use .IsRequired() for NOT NULL and .HasMaxLength() for length constraints.

Example: Ticket Number Must Be Unique & Required

builder.Property(t => t.TicketNumber)
       .IsRequired() // NOT NULL
       .HasMaxLength(20);

builder.HasIndex(t => t.TicketNumber)
       .IsUnique();  // Unique constraint

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Final Configuration File Example (TicketConfiguration.cs)

Here’s a complete example of a configuration file:

public class TicketConfiguration : IEntityTypeConfiguration<Ticket>
{
    public void Configure(EntityTypeBuilder<Ticket> builder)
    {
        builder.HasKey(t => t.Id);

        builder.Property(t => t.TransportationId)
            .IsRequired();

        builder.Property(t => t.SeatId)
            .IsRequired();

        builder.Property(t => t.BuyerId)
            .IsRequired();

        builder.Property(t => t.TravelerId)
            .IsRequired();

        builder.Property(t => t.CreatedAt)
            .IsRequired();

        builder.Property(t => t.CompanionId)
            .IsRequired(false);

        builder.Property(t => t.TicketStatusId)
            .IsRequired();

        builder.Property(t => t.SerialNumber)
            .IsRequired()
            .HasMaxLength(50)
            .IsUnicode(false);

        builder.Property(t => t.Description)
            .HasMaxLength(200)
            .IsUnicode(false);

        // Relationships
        builder.HasOne(t => t.Transportation)
            .WithMany(t => t.Tickets)
            .HasForeignKey(t => t.TransportationId)
            .OnDelete(DeleteBehavior.Restrict);

        builder.HasOne(t => t.Seat)
            .WithMany(s => s.Tickets)
            .HasForeignKey(t => t.SeatId)
            .OnDelete(DeleteBehavior.Restrict);

        builder.HasOne(t => t.Buyer)
            .WithMany(a => a.BoughtTickets)
            .HasForeignKey(t => t.BuyerId)
            .OnDelete(DeleteBehavior.Restrict);

        builder.HasOne(t => t.Traveler)
            .WithMany(p => p.TraveledTickets)
            .HasForeignKey(t => t.TravelerId)
            .OnDelete(DeleteBehavior.Restrict);

        builder.HasOne(t => t.Companion)
            .WithMany()
            .HasForeignKey(t => t.CompanionId)
            .OnDelete(DeleteBehavior.Restrict);

        builder.HasOne(t => t.TicketStatus)
            .WithMany()
            .HasForeignKey(t => t.TicketStatusId)
            .OnDelete(DeleteBehavior.Restrict);
    }
}

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Summary & Best Practices

✅ Store Configuration Files in: Infrastructure/Configurations
✅ Define Foreign Keys: Use HasOne() and WithMany()
✅ Explicitly Define Navigation Properties if the names differ
✅ Column Types: Use .HasColumnType() for nvarchar, date, etc.
✅ Constraints: Use .IsRequired(), .HasMaxLength(), .IsUnique()

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1. Join Tables with Multiple IDs

In many-to-many relationships, a join table is created to link two entities. This join table typically contains foreign keys referencing the primary keys of the two entities involved in the relationship.

Example of a Join Table

Suppose we have two entities, Student and Course, and we want to create a many-to-many relationship between them. We'll create a join table called StudentCourses.

Entities

public class Student : Entity<long>
{
    public required string Name { get; set; }
    public virtual ICollection<StudentCourse> StudentCourses { get; set; }
}

public class Course : Entity<long>
{
    public required string Title { get; set; }
    public virtual ICollection<StudentCourse> StudentCourses { get; set; }
}

public class StudentCourse
{
    public long StudentId { get; set; }
    public virtual Student Student { get; set; }

    public long CourseId { get; set; }
    public virtual Course Course { get; set; }
}

Configuration for Join Table

You would configure the join table using the Fluent API:

public class StudentCourseConfiguration : IEntityTypeConfiguration<StudentCourse>
{
    public void Configure(EntityTypeBuilder<StudentCourse> builder)
    {
        // Composite Primary Key
        builder.HasKey(sc => new { sc.StudentId, sc.CourseId });

        // Foreign Key Relationships
        builder.HasOne(sc => sc.Student)
            .WithMany(s => s.StudentCourses)
            .HasForeignKey(sc => sc.StudentId);

        builder.HasOne(sc => sc.Course)
            .WithMany(c => c.StudentCourses)
            .HasForeignKey(sc => sc.CourseId);
    }
}

Key Points for Join Tables

• Composite Primary Key: The join table uses a composite key made up of both foreign keys.
• Navigation Properties: This enables navigation from Student to Course and vice versa.

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2. Using GUIDs That Should Be Auto-Generated

GUIDs (Globally Unique Identifiers) can be used as primary keys in your entities. In EF Core, you can configure them to auto-generate when a new entity is created.

Example Entity Using GUID

public class SomeEntity
{
    public Guid Id { get; set; } = Guid.NewGuid(); // Auto-generate GUID
    public string Name { get; set; }
}

Configuration for GUID

When configuring an entity with a GUID as the primary key, you don’t need a specific setup in the configuration, but you can enforce that the Id is generated on addition.

builder.Property(e => e.Id)
    .ValueGeneratedOnAdd()
    .HasDefaultValueSql("NEWSEQUENTIALID()"); // Optionally use NEWID() for random GUID

How It Works

• Guid.NewGuid() generates a new GUID when a new entity instance is created.
• Database: If you use NEWSEQUENTIALID() in SQL Server, it generates sequential GUIDs, which can improve indexing performance.

Example Configuration in DbContext

Here's how you might define an entity with GUIDs in your DbContext:

public class ApplicationDbContext : DbContext
{
    public DbSet<SomeEntity> SomeEntities { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<SomeEntity>(builder =>
        {
            builder.HasKey(e => e.Id);
            builder.Property(e => e.Id)
                .ValueGeneratedOnAdd()
                .HasDefaultValueSql("NEWSEQUENTIALID()");
        });
    }
}

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Merge

• Create a PR and merge the current branch with develop

2. Application DBContext and ConnectionString Configurations

Preparation

• Read the documentation: https://learn.microsoft.com/en-us/ef/core/modeling/

Branching

• Create the feature/setup-dbContext branch based on develop

Database Context

• Create ApplicationDBContext
  • Location: Infrastructure/ApplicationDbContext.cs
  • Inherits DbContext
  • Create the constructor like the code below
  • Add the Needed DbSets
  • Override OnModelCreating and OnConfiguring as below

using AlibabaClone.Domain.Aggregates.AccountAggregates;

using Microsoft.EntityFrameworkCore;

namespace AlibabaClone.Infrastructure
{
    public class ApplicationDBContext : DbContext
    {
        public ApplicationDBContext(DbContextOptions<ApplicationDBContext> options) : base(options)
        {

        }

        public DbSet<Account> Accounts { get; set; }
        public DbSet<AccountRole> AccountRoles { get; set; }
        public DbSet<Gender> Genders{ get; set; }
        public DbSet<Person> People { get; set; }
        public DbSet<Role> Roles { get; set; }

		//... Add other DbSets as well

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.ApplyConfigurationsFromAssembly(typeof(ApplicationDBContext).Assembly);
            base.OnModelCreating(modelBuilder);
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseLazyLoadingProxies();
        }
    }
}

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Configuring the Database in ASP.NET Core

📌 **Connection String **

• Modify appsettings.json and add the following. (They might have a type or something... search the web to make sure)

• Adjust the ConnectionString to meet your needs

Option 1:

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=YOUR_SERVER;Database=YourDb;User Id=USERNAME;Password=PASSWORD;Trusted_Connection=True;TrustServerCertificate=True"
  }
}

Option 2:

{
  "ConnectionStrings": {
    "DefaultConnection": "Server=YOUR_SERVER;Database=YourDb;Integrated Security=TRUE;Trusted_Connection=True;TrustServerCertificate=True"
  }
}

• Put this appsettings.json in gitignore if you think is needed

Registering EF Core in Program.cs

• Modify Program.cs

using Infrastructure.Persistence;
using Microsoft.EntityFrameworkCore;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

// Register repositories and Unit of Work
builder.Services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
builder.Services.AddScoped<IUnitOfWork, UnitOfWork>();

var app = builder.Build();
app.Run();

Merge

• Create a PR and merge the current branch with develop

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Migrations and Database Setup

Branching

• Create the feature/migrations branch based on develop

Using Package Manager Console

• Make sure to set the project to Infrastructure
• Make sure you have installed Microsoft.EntityFrameworkCore.Tools
• Run the following command

Add-Migrations InitialCreate

• In case of scuccues:

Update-Database

Merge

• Create a PR and merge the current branch with develop

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