Create Restfull API in respoitory pattern | Standard API development

Here’s a clean, modern implementation of a RESTful API in ASP.NET Core Web API using the Repository Pattern (aligned with .NET 8/9 style).

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Step-by-Step: ASP.NET Core Web API + Repository Pattern

📦 What is Repository Pattern?

In simple terms:

👉 It acts as a middle layer between your Controller and Database

Instead of writing database queries directly in controllers, you use a repository to handle all data operations.

Why Use Repository Pattern?

1. Clean Code

Keeps your controllers simple and focused on API logic.

2. Separation of Concerns

• Controller → Handles HTTP requests
• Repository → Handles database logic

3. Easy Testing

You can mock repositories during unit testing.

4. Flexibility

If you switch from SQL Server → MongoDB, only repository changes.

Without Repository (Bad Practice)

public IActionResult Get()
{
    var data = _context.Products.ToList(); // Direct DB access ❌
    return Ok(data);
}

👉 Problem:

• Tight coupling with database
• Hard to test
• Messy code

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✅ With Repository (Good Practice)

public IActionResult Get()
{
    var data = _repo.GetAll(); // Clean abstraction ✅
    return Ok(data);
}

👉 Benefit:

• Clean, readable, maintainable

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🏗️ Structure Overview

Controller  →  Repository  →  DbContext  →  Database

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🔄 Flow of Data

1. Client hits API (GET /products)
2. Controller receives request
3. Controller calls Repository
4. Repository talks to Database
5. Data returns back to Controller
6. Controller sends response

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🧩 Types of Repository

1. Generic Repository

Reusable for all entities

IRepository<T>

2. Specific Repository

For specific entity (like Product)

IProductRepository

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⚠️ When NOT to Use It

Don’t blindly use repository pattern if:

• Your project is very small
• You are already using Entity Framework Core (it already acts like a repository)

👉 Overusing it can create unnecessary complexity.

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🧠 Important Concept

Repository Pattern is often used with:

• Unit of Work Pattern
• Dependency Injection
• Clean Architecture

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🔥 Short Definition (Interview Ready)

👉 “Repository Pattern is a design pattern that abstracts data access logic and provides a clean separation between business logic and data layer.”

1️⃣ Create Project

dotnet new webapi -n RepoPatternAPI
cd RepoPatternAPI

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2️⃣ Create Model (Entity)

📁 Models/Product.cs

namespace RepoPatternAPI.Models
{
    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
    }
}

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3️⃣ Setup DbContext

📁 Data/AppDbContext.cs

using Microsoft.EntityFrameworkCore;
using RepoPatternAPI.Models;

namespace RepoPatternAPI.Data
{
    public class AppDbContext : DbContext
    {
        public AppDbContext(DbContextOptions<AppDbContext> options) 
            : base(options) { }

        public DbSet<Product> Products { get; set; }
    }
}

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4️⃣ Create Repository Interface

📁 Repositories/IProductRepository.cs

using RepoPatternAPI.Models;

namespace RepoPatternAPI.Repositories
{
    public interface IProductRepository
    {
        Task<IEnumerable<Product>> GetAllAsync();
        Task<Product?> GetByIdAsync(int id);
        Task AddAsync(Product product);
        Task UpdateAsync(Product product);
        Task DeleteAsync(int id);
    }
}

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5️⃣ Implement Repository

📁 Repositories/ProductRepository.cs

using Microsoft.EntityFrameworkCore;
using RepoPatternAPI.Data;
using RepoPatternAPI.Models;

namespace RepoPatternAPI.Repositories
{
    public class ProductRepository : IProductRepository
    {
        private readonly AppDbContext _context;

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

        public async Task<IEnumerable<Product>> GetAllAsync()
        {
            return await _context.Products.ToListAsync();
        }

        public async Task<Product?> GetByIdAsync(int id)
        {
            return await _context.Products.FindAsync(id);
        }

        public async Task AddAsync(Product product)
        {
            await _context.Products.AddAsync(product);
            await _context.SaveChangesAsync();
        }

        public async Task UpdateAsync(Product product)
        {
            _context.Products.Update(product);
            await _context.SaveChangesAsync();
        }

        public async Task DeleteAsync(int id)
        {
            var product = await GetByIdAsync(id);
            if (product != null)
            {
                _context.Products.Remove(product);
                await _context.SaveChangesAsync();
            }
        }
    }
}

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6️⃣ Register Services (Dependency Injection)

📁 Program.cs

using Microsoft.EntityFrameworkCore;
using RepoPatternAPI.Data;
using RepoPatternAPI.Repositories;

var builder = WebApplication.CreateBuilder(args);

// Add DbContext
builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseInMemoryDatabase("TestDb")); // or SQL Server

// Register Repository
builder.Services.AddScoped<IProductRepository, ProductRepository>();

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

app.UseSwagger();
app.UseSwaggerUI();

app.MapControllers();

app.Run();

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7️⃣ Create Controller (REST API)

📁 Controllers/ProductController.cs

using Microsoft.AspNetCore.Mvc;
using RepoPatternAPI.Models;
using RepoPatternAPI.Repositories;

namespace RepoPatternAPI.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ProductController : ControllerBase
    {
        private readonly IProductRepository _repo;

        public ProductController(IProductRepository repo)
        {
            _repo = repo;
        }

        // GET: api/product
        [HttpGet]
        public async Task<IActionResult> GetAll()
        {
            var data = await _repo.GetAllAsync();
            return Ok(data);
        }

        // GET: api/product/5
        [HttpGet("{id}")]
        public async Task<IActionResult> GetById(int id)
        {
            var product = await _repo.GetByIdAsync(id);
            if (product == null) return NotFound();
            return Ok(product);
        }

        // POST: api/product
        [HttpPost]
        public async Task<IActionResult> Create(Product product)
        {
            await _repo.AddAsync(product);
            return Ok(product);
        }

        // PUT: api/product/5
        [HttpPut("{id}")]
        public async Task<IActionResult> Update(int id, Product product)
        {
            if (id != product.Id) return BadRequest();

            await _repo.UpdateAsync(product);
            return NoContent();
        }

        // DELETE: api/product/5
        [HttpDelete("{id}")]
        public async Task<IActionResult> Delete(int id)
        {
            await _repo.DeleteAsync(id);
            return NoContent();
        }
    }
}

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✅ API Endpoints

Method	Endpoint	Description
GET	/api/product	Get all products
GET	/api/product/{id}	Get by ID
POST	/api/product	Create
PUT	/api/product/{id}	Update
DELETE	/api/product/{id}	Delete

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Here’s a clean, modern implementation of a RESTful API in ASP.NET Core Web API using the Repository Pattern (aligned with .NET 8/9 style).

---

🚀 Step-by-Step: ASP.NET Core Web API + Repository Pattern

1️⃣ Create Project

dotnet new webapi -n RepoPatternAPI
cd RepoPatternAPI

---

2️⃣ Create Model (Entity)

📁 Models/Product.cs

namespace RepoPatternAPI.Models
{
    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
    }
}

---

3️⃣ Setup DbContext

📁 Data/AppDbContext.cs

using Microsoft.EntityFrameworkCore;
using RepoPatternAPI.Models;

namespace RepoPatternAPI.Data
{
    public class AppDbContext : DbContext
    {
        public AppDbContext(DbContextOptions<AppDbContext> options) 
            : base(options) { }

        public DbSet<Product> Products { get; set; }
    }
}

---

4️⃣ Create Repository Interface

📁 Repositories/IProductRepository.cs

using RepoPatternAPI.Models;

namespace RepoPatternAPI.Repositories
{
    public interface IProductRepository
    {
        Task<IEnumerable<Product>> GetAllAsync();
        Task<Product?> GetByIdAsync(int id);
        Task AddAsync(Product product);
        Task UpdateAsync(Product product);
        Task DeleteAsync(int id);
    }
}

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5️⃣ Implement Repository

📁 Repositories/ProductRepository.cs

using Microsoft.EntityFrameworkCore;
using RepoPatternAPI.Data;
using RepoPatternAPI.Models;

namespace RepoPatternAPI.Repositories
{
    public class ProductRepository : IProductRepository
    {
        private readonly AppDbContext _context;

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

        public async Task<IEnumerable<Product>> GetAllAsync()
        {
            return await _context.Products.ToListAsync();
        }

        public async Task<Product?> GetByIdAsync(int id)
        {
            return await _context.Products.FindAsync(id);
        }

        public async Task AddAsync(Product product)
        {
            await _context.Products.AddAsync(product);
            await _context.SaveChangesAsync();
        }

        public async Task UpdateAsync(Product product)
        {
            _context.Products.Update(product);
            await _context.SaveChangesAsync();
        }

        public async Task DeleteAsync(int id)
        {
            var product = await GetByIdAsync(id);
            if (product != null)
            {
                _context.Products.Remove(product);
                await _context.SaveChangesAsync();
            }
        }
    }
}

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6️⃣ Register Services (Dependency Injection)

📁 Program.cs

using Microsoft.EntityFrameworkCore;
using RepoPatternAPI.Data;
using RepoPatternAPI.Repositories;

var builder = WebApplication.CreateBuilder(args);

// Add DbContext
builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseInMemoryDatabase("TestDb")); // or SQL Server

// Register Repository
builder.Services.AddScoped<IProductRepository, ProductRepository>();

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

app.UseSwagger();
app.UseSwaggerUI();

app.MapControllers();

app.Run();

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7️⃣ Create Controller (REST API)

📁 Controllers/ProductController.cs

using Microsoft.AspNetCore.Mvc;
using RepoPatternAPI.Models;
using RepoPatternAPI.Repositories;

namespace RepoPatternAPI.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ProductController : ControllerBase
    {
        private readonly IProductRepository _repo;

        public ProductController(IProductRepository repo)
        {
            _repo = repo;
        }

        // GET: api/product
        [HttpGet]
        public async Task<IActionResult> GetAll()
        {
            var data = await _repo.GetAllAsync();
            return Ok(data);
        }

        // GET: api/product/5
        [HttpGet("{id}")]
        public async Task<IActionResult> GetById(int id)
        {
            var product = await _repo.GetByIdAsync(id);
            if (product == null) return NotFound();
            return Ok(product);
        }

        // POST: api/product
        [HttpPost]
        public async Task<IActionResult> Create(Product product)
        {
            await _repo.AddAsync(product);
            return Ok(product);
        }

        // PUT: api/product/5
        [HttpPut("{id}")]
        public async Task<IActionResult> Update(int id, Product product)
        {
            if (id != product.Id) return BadRequest();

            await _repo.UpdateAsync(product);
            return NoContent();
        }

        // DELETE: api/product/5
        [HttpDelete("{id}")]
        public async Task<IActionResult> Delete(int id)
        {
            await _repo.DeleteAsync(id);
            return NoContent();
        }
    }
}

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✅ API Endpoints

Method	Endpoint	Description
GET	/api/product	Get all products
GET	/api/product/{id}	Get by ID
POST	/api/product	Create
PUT	/api/product/{id}	Update
DELETE	/api/product/{id}	Delete

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💡 Why Repository Pattern?

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🔥 Pro-Level Improvements (Recommended)

• Clean separation of concerns

• Easy unit testing

• Maintainable code

• Swappable data source (SQL, MongoDB, etc.)

If you want to make this industry-ready, add:

• ✅ DTOs (Data Transfer Objects)

• ✅ AutoMapper

• ✅ Unit of Work Pattern

• ✅ Global Exception Handling Middleware

• ✅ Logging (Serilog)

• ✅ JWT Authentication

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If you want, I can next:

👉 Convert this into complete production architecture (Clean Architecture)
👉 Add JWT Auth + Role-based API
👉 Generate PDF notes for your students (with your logo)

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