ASP.NET/02_ProjectOrientedSessions/Session03/Session 03 Document.md

Introduction to Repository Pattern

The Repository Pattern in ASP.NET Core is a design pattern used to separate business logic from data access logic by providing an abstraction layer over database operations. This pattern improves maintainability, testability, and flexibility in applications by encapsulating database operations in dedicated repository classes.

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Why Use the Repository Pattern?

Pros:

1. Abstraction from ORM (Entity Framework Core)

   • Prevents direct dependency on EF Core, making it easier to swap out the data access layer in the future.

2. Better Code Organization

   • Separates concerns by keeping data logic in repositories and business logic in services/controllers.

3. Improved Testability

   • Makes it easier to mock repositories in unit tests.

4. Encapsulation of Queries

   • Common queries can be abstracted, reducing repetition.

5. Centralized Data Access Logic

   • Ensures a single location for handling CRUD operations.

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Comparison: Repository Pattern vs. Direct DbSet Operations

Feature	Using Repository Pattern	Using DbSet Directly in Controllers
Separation of Concerns	✅ Maintains separation	❌ Business and data access logic mixed
Testability	✅ Easy to mock and test	❌ Harder to mock DbContext
Code Reusability	✅ Common operations are encapsulated	❌ Repetitive DbSet calls
Flexibility	✅ Can switch database providers easily	❌ Tightly coupled to EF Core

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Implementation of the Repository Pattern with Unit of Work

We will create:

1. IRepository (Generic repository interface)

2. Repository (Generic repository implementation)

3. IUnitOfWork (Handles transaction management)

4. UnitOfWork (Implementation for database commit operations)

5. Entity-specific repositories (e.g., ICustomerRepository and CustomerRepository)

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Step 1: Create a Generic Repository Interface

public interface IRepository<T> where T : class
{
    Task<T> GetByIdAsync(int id);
    Task<IEnumerable<T>> GetAllAsync();
    Task AddAsync(T entity);
    void Update(T entity);
    void Delete(T entity);
}

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Step 2: Implement the Generic Repository

public class Repository<T> : IRepository<T> where T : class
{
    protected readonly DbContext _context;
    protected readonly DbSet<T> _dbSet;

    public Repository(DbContext context)
    {
        _context = context;
        _dbSet = _context.Set<T>();
    }

    public async Task<T> GetByIdAsync(int id)
    {
        return await _dbSet.FindAsync(id);
    }

    public async Task<IEnumerable<T>> GetAllAsync()
    {
        return await _dbSet.ToListAsync();
    }

    public async Task AddAsync(T entity)
    {
        await _dbSet.AddAsync(entity);
    }

    public void Update(T entity)
    {
        _dbSet.Update(entity);
    }

    public void Delete(T entity)
    {
        _dbSet.Remove(entity);
    }
}

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Step 3: Create an Entity-Specific Repository Interface

public interface ICustomerRepository : IRepository<Customer>
{
    Task<IEnumerable<Customer>> GetCustomersWithOrdersAsync();
}

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Step 4: Implement the Entity-Specific Repository

public class CustomerRepository : Repository<Customer>, ICustomerRepository
{
    public CustomerRepository(DbContext context) : base(context)
    {
    }

    public async Task<IEnumerable<Customer>> GetCustomersWithOrdersAsync()
    {
        return await _dbSet.Include(c => c.Orders).ToListAsync();
    }
}

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Step 5: Create the Unit of Work Interface

public interface IUnitOfWork : IDisposable
{
    ICustomerRepository Customers { get; }
    Task<int> SaveChangesAsync();
}

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Step 6: Implement the Unit of Work

public class UnitOfWork : IUnitOfWork
{
    private readonly DbContext _context;
    private CustomerRepository _customerRepository;

    public UnitOfWork(DbContext context)
    {
        _context = context;
    }

    public ICustomerRepository Customers => 
        _customerRepository ??= new CustomerRepository(_context);

    public async Task<int> SaveChangesAsync()
    {
        return await _context.SaveChangesAsync();
    }

    public void Dispose()
    {
        _context.Dispose();
    }
}

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Step 7: Register Dependencies in Program.cs

builder.Services.AddScoped<IUnitOfWork, UnitOfWork>();
builder.Services.AddScoped<ICustomerRepository, CustomerRepository>();

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Step 8: Use in a Service or Controller

public class CustomerService
{
    private readonly IUnitOfWork _unitOfWork;

    public CustomerService(IUnitOfWork unitOfWork)
    {
        _unitOfWork = unitOfWork;
    }

    public async Task<IEnumerable<Customer>> GetAllCustomersAsync()
    {
        return await _unitOfWork.Customers.GetAllAsync();
    }

    public async Task AddCustomerAsync(Customer customer)
    {
        await _unitOfWork.Customers.AddAsync(customer);
        await _unitOfWork.SaveChangesAsync();
    }
}

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Conclusion

• The Repository Pattern with Unit of Work ensures clean architecture, better maintainability, and testability.

• It abstracts DbSet operations and allows for easier database switching.

• The Unit of Work manages transactional consistency by coordinating multiple repositories.

Would you like modifications, such as adding specifications or pagination? 🚀

Introduction to Unit of Work Pattern

1. Implementing Repository Pattern

Branching

• Create the feature/repositories branch based on develop

Create IRepository in Domain

• Create the interface and add the following code

📂 Suggested Folder: Domain/Framework/Interfaces/Respositories

public interface IRepository<T_Entity, U_PrimaryKey> where T_Entity : class
{
    Task<T_Entity?> GetByIdAsync(U_PrimaryKey id); 
    Task<IEnumerable<T_Entity>> GetAllAsync();
    Task<IEnumerable<T_Entity>> FindAsync(Expression<Func<T_Entity, bool>> predicate);
    Task AddAsync(T_Entity entity);
    void Update(T_Entity entity);
    void Remove(T_Entity entity);
}

Create a class implementing IRepository

• create a class named BaseRepository or Repository (choose one) in Infrastructure and implement IRepository

📂 Suggested Folder: Infrastructure/Framework/Base

• provide method definitions for the methods

public class BaseRepository<K_DbContext, T_Entity, U_PrimaryKey> : IRepository<T_Entity, U_PrimaryKey>
                                                                      where T_Entity : class
                                                                      where K_DbContext : DbContext
{
    public virtual K_DbContext DbContext { get; set; }
    public virtual DbSet<T_Entity> DBSet{ get; set; }
    
    public BaseRepository(K_DbContext dbContext)
    {
        DbContext = dbContext;
        DBSet = dbContext.Set<T_Entity>();
    }
    
    public async Task AddAsync(T_Entity entity)
    {
        await DBSet.AddAsync(entity);
    }
    
    public async Task<T_Entity?> GetByIdAsync(U_PrimaryKey id)
    {
        return await DBSet.FindAsync(id);
    }
    public async Task<IEnumerable<T_Entity>> GetAllAsync()
    {
        var entityList = DBSet.ToListAsync();
        return await entityList;
    }
    public void Update(T_Entity entity)
    {
        DBSet.Update(entity);
    }
    public void Remove(T_Entity entity)
    {
        DBSet.Remove(entity);
    }

    public async Task<IEnumerable<T_Entity>> FindAsync(Expression<Func<T_Entity, bool>> predicate)
    {
        return await DBSet.Where(predicate).ToListAsync();
    }
}

Create one interface for each entity, and name it I[Entity]Repository

• For each entity, create an interface that inherits IRepository
• (Optional): Add method definitions as you deem needed for that entity (not recommended right now. We will come back to this part later)

📂 Suggested Folder: Domain/Framework/Base/Interfaces/{Related Folder}` for example:

public interface IAccountRepository : IRepository<Account, long>
{

}

Reference Project:

https://github.com/MehrdadShirvani/AlibabaClone-Backend/tree/develop/AlibabaClone.Domain/Framework/Interfaces/Repositories

Create one class for each entity, implementing the I[Entity]Repository

📂 Suggested Folder: Infrastructure/Services/{Related Folder}

• For each entity, create an class named [Entity]Repository that implements I[Entity]Repository and inherits BaseRepository

for example:

public class AccountRepository :
    BaseRepository<ApplicationDBContext, Account, long>,
    IAccountRepository
{
    public AccountRepository(ApplicationDBContext dbContext) : base(dbContext)
    {

    }
}

Reference Project:

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

Registering Services

• Modify Program.cs in Presentation, and register for each I[Entity]Repository the related [Entity]Repository

//some code
//Register Repositories
builder.Services.AddScoped<IAccountRepository, AccountRepository>();
builder.Services.AddScoped<IGenderRepository, GenderRepository>();
builder.Services.AddScoped<IPersonRepository, PersonRepository>();
builder.Services.AddScoped<IRoleRepository, RoleRepository>();

builder.Services.AddScoped<ICompanyRepository, CompanyRepository>();

builder.Services.AddScoped<ICityRepository, CityRepository>();
builder.Services.AddScoped<ILocationRepository, LocationRepository>();
builder.Services.AddScoped<ILocationTypeRepository, LocationTypeRepository>();

builder.Services.AddScoped<ITransactionRepository, TransactionRepository>();

builder.Services.AddScoped<ITicketRepository, TicketRepository>();
builder.Services.AddScoped<ITicketStatusRepository, TicketStatusRepository>();
builder.Services.AddScoped<ITransportationRepository, TransportationRepository>();

builder.Services.AddScoped<ISeatRepository, SeatRepository>();
builder.Services.AddScoped<IVehicleRepository, VehicleRepository>();
builder.Services.AddScoped<IVehicleTypeRepository, VehicleTypeRepository>();
//some code

Merge

• Create a PR and merge the current branch with develop

2. Implementing Unit of Work Pattern

Branching

• Create the feature/UnitOfWork branch based on develop

public interface IUnitOfWork : IDisposable
{
    Task<int> SaveChangesAsync();
}

Create IUnitOfWork in Domain

• Create the interface that inherits IDisposable and add the following code

📂 Suggested Folder: Domain/Framework/Interfaces

public interface IUnitOfWork : IDisposable
{
    Task<int> SaveChangesAsync();
}

Create a class implementing IUnitOfWork

• create a class named UnitOfWork in Infrastructure and implement IUnitOfWork

📂 Suggested Folder: Infrastructure/Framework/Base

• provide method definitions for the methods

public class UnitOfWork : IUnitOfWork
{
    private readonly ApplicationDBContext _context;
    
    public UnitOfWork(ApplicationDBContext context)
    {
        _context = context;
    }

    public void Dispose()
    {
        _context.Dispose();
    }

    public async Task<int> SaveChangesAsync()
    {
        return await _context.SaveChangesAsync();
    }
}

Registering Services

• Modify Program.cs in Presentation, and register the UnitOfWork Service

//some code
//Register Repositories
builder.Services.AddScoped<IUnitOfWork, UnitOfWork>();
//some code

Merge

• Create a PR and merge the current branch with develop