ASP.NET - Repository Pattern vs Unit of Work in ASP.NET Core

The Repository Pattern and Unit of Work are two important design patterns used in ASP.NET Core applications to manage data access logic in a clean, maintainable, and testable way. They are often used together, especially in applications that use ORMs like Entity Framework Core.

Repository Pattern

The Repository Pattern acts as an abstraction layer between the application and the data access logic. Instead of directly interacting with the database using DbContext throughout your code, you create a repository that encapsulates all data operations.

Purpose

To isolate data access code from business logic
To make the code more maintainable and testable
To provide a consistent interface for accessing data

Example Concept

Instead of writing database queries directly in controllers or services, you define a repository interface:

public interface IProductRepository
{
    IEnumerable<Product> GetAll();
    Product GetById(int id);
    void Add(Product product);
    void Update(Product product);
    void Delete(int id);
}

Then implement it:

public class ProductRepository : IProductRepository
{
    private readonly AppDbContext _context;

    public ProductRepository(AppDbContext context)
    {
        _context = context;
    }

    public IEnumerable<Product> GetAll()
    {
        return _context.Products.ToList();
    }

    public Product GetById(int id)
    {
        return _context.Products.Find(id);
    }

    public void Add(Product product)
    {
        _context.Products.Add(product);
    }

    public void Update(Product product)
    {
        _context.Products.Update(product);
    }

    public void Delete(int id)
    {
        var product = _context.Products.Find(id);
        if (product != null)
        {
            _context.Products.Remove(product);
        }
    }
}

Advantages

Promotes separation of concerns
Easier unit testing using interfaces and mocks
Centralized data access logic

Limitations

Can add unnecessary abstraction when using Entity Framework Core, which already behaves like a repository
May lead to too many classes in large applications

Unit of Work Pattern

The Unit of Work Pattern is responsible for managing transactions and coordinating multiple repository operations into a single logical unit.

Purpose

To ensure that a group of operations either all succeed or all fail
To manage database transactions efficiently
To reduce multiple database calls

Example Concept

A Unit of Work typically wraps the DbContext and exposes repositories:

public interface IUnitOfWork
{
    IProductRepository Products { get; }
    IOrderRepository Orders { get; }
    int Complete();
}

Implementation:

public class UnitOfWork : IUnitOfWork
{
    private readonly AppDbContext _context;

    public IProductRepository Products { get; private set; }
    public IOrderRepository Orders { get; private set; }

    public UnitOfWork(AppDbContext context)
    {
        _context = context;
        Products = new ProductRepository(_context);
        Orders = new OrderRepository(_context);
    }

    public int Complete()
    {
        return _context.SaveChanges();
    }
}

How It Works

Multiple repositories share the same DbContext
Changes are tracked but not immediately saved
Calling Complete() commits all changes in a single transaction

Key Differences Between Repository and Unit of Work

Aspect	Repository Pattern	Unit of Work
Responsibility	Handles data access for a specific entity	Manages transactions across repositories
Scope	Single entity or aggregate	Multiple repositories
Purpose	Encapsulation of CRUD operations	Coordination and consistency
Save Changes	Usually not responsible for saving	Responsible for committing changes

When Used Together

In real-world ASP.NET Core applications, both patterns are often combined:

Repositories handle entity-specific operations
Unit of Work manages transaction boundaries

Example flow:

Service calls multiple repositories
Each repository performs operations
Unit of Work commits all changes together

When to Use and When Not to Use

Use These Patterns When:

Building large-scale or enterprise applications
You need strict separation between business logic and data access
You want better testability and maintainability
You are working with multiple data sources or complex transactions

Avoid or Simplify When:

Using simple CRUD applications
Entity Framework Core is sufficient on its own
Over-engineering becomes a concern

Conclusion

The Repository Pattern focuses on organizing and abstracting data access logic, while the Unit of Work ensures that multiple operations are treated as a single transaction. Together, they help build clean, scalable, and maintainable ASP.NET Core applications, but they should be applied thoughtfully to avoid unnecessary complexity.