ASP.NET

Session02 Backend

6 min read

🛠️ Task Checklist

🚧 Branching (Configurations)

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

Preparation

Create configuration classes

📂 Suggested Folder: Infrastructure/Configurations

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

Where Should You Place Configuration Files?

✅ Best Practice: Place all configuration files in the Infrastructure layer.

Reason:

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

Use this as a reference:

reference

Explanations and Details

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.

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
    }
}

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.

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"

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

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.

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);
    }
}

Final Configuration File Example (TicketConfiguration.cs)

Here’s an example of a configuration file:

public class TicketConfiguration : IEntityTypeConfiguration<Ticket>
{
    public void Configure(EntityTypeBuilder<Ticket> builder)
    {
        builder.HasKey(t => t.Id);
        builder.Property(a => a.Id)
            .ValueGeneratedOnAdd();
 
        builder.Property(t => t.TicketOrderId)
            .IsRequired();
 
        builder.Property(t => t.SeatId)
            .IsRequired();
 
        builder.Property(t => t.TravelerId)
            .IsRequired();
 
        builder.Property(t => t.CreatedAt)
            .IsRequired();
 
        builder.Property(t => t.CanceledAt)
            .IsRequired(false);
 
        builder.Property(t => t.CompanionId)
            .IsRequired(false);
 
        builder.Property(t => t.TicketStatusId)
            .IsRequired();
 
        builder.Property(t => t.SerialNumber)
            .IsRequired()
            .HasMaxLength(50)
            .IsUnicode(false);
        builder.HasIndex(x => x.SerialNumber).IsUnique();
 
 
        builder.Property(t => t.Description)
            .HasMaxLength(200)
            .IsUnicode(false);
 
        // Relationships
        builder.HasOne(t => t.TicketOrder)
            .WithMany(t => t.Tickets)
            .HasForeignKey(t => t.TicketOrderId)
            .OnDelete(DeleteBehavior.Restrict);
 
        builder.HasOne(t => t.Seat)
            .WithMany(s => s.Tickets)
            .HasForeignKey(t => t.SeatId)
            .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);
    }
}

🚧 Merge

  • Create a PR and merge the current branch with develop

🚧 Branching (Application DBContext and Connection String Configurations)

Preparation

Branching

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

Database Context

📂 Suggested Folder: `Infrastructure/ApplicationDbContext.cs

  • Create ApplicationDBContext
    • Inherits DbContext
    • Create the constructor like the code below
    • Add the necessary DbSets
    • Override OnModelCreating and OnConfiguring as below
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<BankAccountDetail> BankAccountDetails{ get; set; }
    public DbSet<Person> People { get; set; }
    public DbSet<Role> Roles { get; set; }
 
    public DbSet<Company> Companies { get; set; }
 
    public DbSet<City> Cities { get; set; }
    public DbSet<Location> Locations { get; set; }
    public DbSet<LocationType> LocationTypes{ get; set; }
 
    public DbSet<Transaction> Transactions { get; set; }
    public DbSet<Coupon> Coupons{ get; set; }
    public DbSet<TransactionType> TransactionTypes { get; set; }
 
    public DbSet<Ticket> Tickets { get; set; }
    public DbSet<TicketOrder> TicketOrders { get; set; }
    public DbSet<TicketStatus> TicketStatuses { get; set; }
    public DbSet<Transportation> Transportations { get; set; }
 
    public DbSet<Seat> Seats { get; set; }
    public DbSet<Vehicle> Vehicles { get; set; }
    public DbSet<VehicleType> VehicleTypes { get; set; }
 
 
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.UseCollation("Persian_100_CI_AI");
        modelBuilder.ApplyConfigurationsFromAssembly(typeof(ApplicationDBContext).Assembly);
        base.OnModelCreating(modelBuilder);
    }
 
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        optionsBuilder.UseLazyLoadingProxies();
    }
}

Configuring the Database in ASP.NET Core

📌 Connection String

  • Modify appsettings.json and add the following.
  • Adjust the Connection String to meet your needs

Option 1:

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

Option 2:

{
  "ConnectionStrings": {
  "DefaultConnection": "Server=YOUR_SERVER;Database=YourDb;Integrated Security=True;TrustServerCertificate=True;"
	}
}
  • Put this appsettings.json in gitignore

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

🚧 Merge

  • Create a PR and merge the current branch with develop

🚧Branching (Migrations and Database Setup)

  • 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-Migration InitialCreate
  • In case of succus:
Update-Database

🚧Merge

  • Create a PR and merge the current branch with develop

🧠 Hints & Notes

🙌 Acknowledgements

  • ChatGPT for snippet refinement and explanations

🔍 References

Session02 Additional Info

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