All About Repository Pattern in C# .NET
Asharib Kamal
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Introduction to Repository Pattern
The Repository Pattern is a design pattern that mediates between the domain and data mapping layers using a collection-like interface for accessing domain objects. Its primary purpose is to abstract the data access layer from the business logic layer, ensuring a clear separation of concerns and making the code more maintainable and testable. The Repository Pattern has been a staple in software development for many years and is widely used in .NET applications.
Key Features of Repository Pattern
1. Abstraction: Provides an abstraction layer over the data access logic, making it easier to change the underlying data source without affecting the business logic.
2. Separation of Concerns: Separates the data access logic from the business logic, promoting cleaner and more maintainable code.
3. Testability: Facilitates unit testing by allowing the use of mock repositories.
4. Centralized Data Access: Centralizes the data access logic, making it easier to manage and maintain.
5. Consistency: Ensures consistency in data access across the application.
Latest Version
The concept of the Repository Pattern itself does not have versions, but its implementation can vary depending on the .NET version. With .NET 5, .NET 6, and the latest .NET 7, the implementation of the Repository Pattern can leverage the new features and improvements in the framework.
How to Use Repository Pattern
1. Creating the Repository Interface:
Define a generic repository interface that outlines the basic CRUD operations.
public interface IRepository<T> where T : class
{
IEnumerable<T> GetAll();
T GetById(int id);
void Add(T entity);
void Update(T entity);
void Delete(int id);
}
2. Implementing the Repository Interface:
Create a concrete class that implements the repository interface.
public class Repository<T> : IRepository<T> where T : class
{
private readonly DbContext _context;
private readonly DbSet<T> _dbSet;
public Repository(DbContext context)
{
_context = context;
_dbSet = context.Set<T>();
}
public IEnumerable<T> GetAll()
{
return _dbSet.ToList();
}
public T GetById(int id)
{
return _dbSet.Find(id);
}
public void Add(T entity)
{
_dbSet.Add(entity);
_context.SaveChanges();
}
public void Update(T entity)
{
_dbSet.Attach(entity);
_context.Entry(entity).State = EntityState.Modified;
_context.SaveChanges();
}
public void Delete(int id)
{
T entity = _dbSet.Find(id);
if (entity != null)
{
_dbSet.Remove(entity);
_context.SaveChanges();
}
}
}
3. Using the Repository in a Service:
Create a service that uses the repository to perform data access operations.
public class ProductService
{
private readonly IRepository<Product> _productRepository;
public ProductService(IRepository<Product> productRepository)
{
_productRepository = productRepository;
}
public IEnumerable<Product> GetAllProducts()
{
return _productRepository.GetAll();
}
public Product GetProductById(int id)
{
return _productRepository.GetById(id);
}
public void AddProduct(Product product)
{
_productRepository.Add(product);
}
public void UpdateProduct(Product product)
{
_productRepository.Update(product);
}
public void DeleteProduct(int id)
{
_productRepository.Delete(id);
}
}
Benefits of Using Repository Pattern
1. Decoupling: Decouples the business logic from the data access logic, leading to more modular and maintainable code.
2. Testability: Makes it easier to unit test the business logic by allowing the use of mock repositories.
3. Flexibility: Provides flexibility to switch data sources or data access methods without changing the business logic.
4. Maintainability: Centralizes data access logic, making it easier to maintain and update.
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5. Consistency: Ensures consistent data access patterns across the application.
Code Examples
Basic Repository Pattern Example:
public interface ICustomerRepository
{
IEnumerable<Customer> GetAllCustomers();
Customer GetCustomerById(int id);
void AddCustomer(Customer customer);
void UpdateCustomer(Customer customer);
void DeleteCustomer(int id);
}
public class CustomerRepository : ICustomerRepository
{
private readonly DbContext _context;
public CustomerRepository(DbContext context)
{
_context = context;
}
public IEnumerable<Customer> GetAllCustomers()
{
return _context.Set<Customer>().ToList();
}
public Customer GetCustomerById(int id)
{
return _context.Set<Customer>().Find(id);
}
public void AddCustomer(Customer customer)
{
_context.Set<Customer>().Add(customer);
_context.SaveChanges();
}
public void UpdateCustomer(Customer customer)
{
_context.Set<Customer>().Attach(customer);
_context.Entry(customer).State = EntityState.Modified;
_context.SaveChanges();
}
public void DeleteCustomer(int id)
{
Customer customer = _context.Set<Customer>().Find(id);
if (customer != null)
{
_context.Set<Customer>().Remove(customer);
_context.SaveChanges();
}
}
}
When to Use the Repository Pattern
- When you need to decouple the business logic from the data access logic.
- When you want to centralize data access logic for easier maintenance and consistency.
- When you need to switch data sources or data access methods without affecting the business logic.
- When you need to facilitate unit testing of the business logic.
Difference Between Repository Pattern and Other Patterns
- Repository Pattern vs. Data Mapper Pattern: The Repository Pattern abstracts data access and provides a collection-like interface, while the Data Mapper Pattern directly maps database tables to domain objects.
- Repository Pattern vs. Active Record Pattern: The Repository Pattern separates data access logic from the domain model, while the Active Record Pattern combines data access logic with the domain model.
- Repository Pattern vs. Unit of Work Pattern: The Repository Pattern deals with a single entity or aggregate, while the Unit of Work Pattern manages changes across multiple entities.
Interview Questions and Answers
Q1: What is the Repository Pattern?
A1: The Repository Pattern is a design pattern that provides an abstraction layer over data access logic, separating it from business logic and promoting cleaner, more maintainable code.
Q2: What are the benefits of using the Repository Pattern?
A2: Benefits include decoupling, testability, flexibility, maintainability, and consistency in data access.
Q3: How do you implement the Repository Pattern in C#?
A3: By defining a repository interface, creating a concrete class that implements the interface, and using the repository in services to perform data access operations.
Q4: What is the difference between the Repository Pattern and the Unit of Work Pattern?
A4: The Repository Pattern deals with individual entities or aggregates, while the Unit of Work Pattern manages changes across multiple entities, ensuring consistency.
Q5: When should you use the Repository Pattern?
A5: Use it when you need to decouple business logic from data access logic, centralize data access, facilitate unit testing, and ensure consistent data access patterns.