ASP.NET/ProjectOrientedSessions/Session01/Session01 Backend.md

Branching

• Create the develop branch
• Create the feature/domain-entities branch based on develop

IEntity.cs

• Create the IEntity interface

Location: Domain Project > Framework > Interfaces

public interface IEntity<TKey>
{
    public TKey Id { get; set; }
}

Entity.cs

• Create the Entity class

Location: Domain Project > Framework > Base

public class Entity<TKey> : IEntity<TKey>
{
    public TKey Id{ get; set; }
}

Why do we need IEntity and Entity? (Chat GPT):

this approach is valid and commonly used in Domain-Driven Design (DDD) and Clean Architecture. It provides consistency, reusability, and common functionality across all entities.

Create Entities

Location: Domain Project > Aggregates > (RelatedFolder)

They all (with the exception of join tables) should inherit Entity, and you should specify the datatype of the Id

Use the latest version of ERD to specify the properties

You can use this project as a reference:

https://github.com/MehrdadShirvani/AlibabaClone-Backend/tree/develop/AlibabaClone.Domain/Aggregates

Link to the ERD:

https://github.com/TheOrderOfPhoenix/ASP.NET/tree/main/02_ProjectOrientedSessions/docs

One Example:

public class Account : Entity<long>
{
    public required string PhoneNumber { get; set; }
    public required string Password { set; get; }
    public string? Email { get; set; }
    public long? PersonId { get; set; }
}

Add Navigation Properties

What is a navigation property? (the following pieces of code are just there for educational purposes)

🔹 Navigation Properties in Entity Framework Core: Everything You Need to Know

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📌 What Are Navigation Properties?

Navigation properties in Entity Framework Core (EF Core) represent relationships between entities. They allow you to navigate (follow) the relationships between different tables using C# objects instead of writing SQL joins manually.

For example, if you have a Ticket entity related to a Buyer, the navigation property allows you to access the buyer from a ticket without writing a separate SQL query.

---

🔹 Types of Navigation Properties

Navigation properties can be of two types:

Relationship Type	Description
Reference Navigation Property	Represents a single entity related to another (one-to-one or many-to-one)
Collection Navigation Property	Represents a list of related entities (one-to-many or many-to-many)

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🔹 How to Define Navigation Properties?

🔹 One-to-Many Example

A Buyer can have multiple Tickets, but each Ticket belongs to one Buyer.

public class Buyer
{
    public int Id { get; set; }
    public string Name { get; set; }

    // Navigation Property (One Buyer → Many Tickets)
    public virtual ICollection<Ticket> Tickets { get; set; } = new List<Ticket>();
}

public class Ticket
{
    public int Id { get; set; }
    public int BuyerId { get; set; }

    // Navigation Property (Many Tickets → One Buyer)
    public virtual Buyer Buyer { get; set; }
}

🔹 One-to-One Example

A Ticket can have only one Transaction, and a Transaction belongs to exactly one Ticket.

public class Ticket
{
    public int Id { get; set; }

    // One-to-One Navigation Property
    public virtual Transaction Transaction { get; set; }
}

public class Transaction
{
    public int Id { get; set; }
    public int TicketId { get; set; }

    // One-to-One Navigation Property
    public virtual Ticket Ticket { get; set; }
}

🔹 Many-to-Many Example

A Buyer can buy many Tickets, and each Ticket can be bought by many Buyers (if resale is allowed).

public class Buyer
{
    public int Id { get; set; }
    public string Name { get; set; }

    // Many-to-Many Navigation Property
    public virtual ICollection<Ticket> Tickets { get; set; } = new List<Ticket>();
}

public class Ticket
{
    public int Id { get; set; }

    // Many-to-Many Navigation Property
    public virtual ICollection<Buyer> Buyers { get; set; } = new List<Buyer>();
}

Add the needed navigation properties inside entities

• Figure out what navigation properties are needed based on the ERD, and use this project as a reference: https://github.com/MehrdadShirvani/AlibabaClone-Backend/tree/develop/AlibabaClone.Domain/Aggregates
• Don't forget to mark all the navigation properties as virtual

Add Packages to Infrastructure Project

• Add Microsoft.EntityFrameworkCore.Proxies to Infrastructure Project

Merge

• Create a PR and merge the current branch with develop