What is the Repository Pattern? When and why to use it?

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ICSM Computer · Answer

What is the Repository Pattern in C#?
The Repository Pattern is a design pattern that acts as a
mediator between the business logic and the data access layer. It provides a consistent way to
access, manage, and query data, while hiding the details of data storage.
Definition
A repository is a collection-like interface for accessing domain objects, centralizing data logic or querying logic to keep the application clean and maintainable.
Purpose of Repository Pattern
Encapsulate data access logicPromote separation of concernsImprove testability (mocking the repository)Enable switching between different data sources (e.g., from SQL to NoSQL)Reduce code duplication for common data operations
Structure of Repository Pattern
Controller → Service/Business Layer → Repository → Data Source (DB)
Typical Repository Interface
public interface IRepositoryandlt;Tandgt;
{
    T GetById(int id);
    IEnumerableandlt;Tandgt; GetAll();
    void Add(T entity);
    void Delete(T entity);
    void Update(T entity);
}
Concrete Implementation Example
public class UserRepository : IRepositoryandlt;Userandgt;
{
    private readonly DbContext _context;
    public UserRepository(DbContext context)
    {
        _context = context;
    }
    public User GetById(int id) =andgt; _context.Users.Find(id);
    public IEnumerableandlt;Userandgt; GetAll() =andgt; _context.Users.ToList();
    public void Add(User user) =andgt; _context.Users.Add(user);
    public void Delete(User user) =andgt; _context.Users.Remove(user);
    public void Update(User user) =andgt; _context.Users.Update(user);
}
When to Use the Repository Pattern
Situation
Use Repository Pattern?
Complex data logic in controllers
✅ Yes
Need to unit test business logic
✅ Yes
Want to abstract away EF Core
✅ Yes
Simple CRUD-only apps
❌ May be overkill
Benefits
Decouples business logic from data logicMakes code more readable and maintainableSupports unit testing with mock repositoriesPromotes DRY (Don't Repeat Yourself) principle
Drawbacks
Can introduce unnecessary abstraction in simple applicationsIf overused, may lead to code duplication or complexityWith EF Core, the DbContext already acts like a repository
Summary
Aspect
Repository Pattern
Main Goal
Abstract data access logic
Improves
Testability, maintainability
Best For
Medium to large apps with business logic
Not Ideal For
Simple apps with only CRUD
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What is the Repository Pattern? When and why to use it?

Anubhav Kumar

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1 Answers

What is the Repository Pattern in C#?

Definition

Purpose of Repository Pattern

Structure of Repository Pattern

Typical Repository Interface

Concrete Implementation Example

When to Use the Repository Pattern

Benefits

Drawbacks

Summary

Liked By

Situation	Use Repository Pattern?
Complex data logic in controllers	✅ Yes
Need to unit test business logic	✅ Yes
Want to abstract away EF Core	✅ Yes
Simple CRUD-only apps	❌ May be overkill

Aspect	Repository Pattern
Main Goal	Abstract data access logic
Improves	Testability, maintainability
Best For	Medium to large apps with business logic
Not Ideal For	Simple apps with only CRUD