Architectural Patterns in C#: Turning Chaos into Order

Architectural Patterns in C#: Don't Let Your Code Turn into Spaghetti

Every C# developer sooner or later faces a moment when their project starts to resemble a plate of overcooked pasta. Methods that are 500 lines long, classes that "know everything," and bugs that multiply faster than rabbits. Sound familiar? It's time to talk about architectural patterns in C#.

In this article, we won't give boring lectures. We'll break down which C# architectural patterns actually save projects, show C# code examples, and provide clear selection criteria. Let's go!

MVC Pattern: A Classic That Never Gets Old

Model-View-Controller (MVC) is perhaps the most popular architectural pattern in C# for web applications. Its main idea is to separate responsibilities into three pillars: data (Model), display (View), and control logic (Controller).

How Does It Work in Practice?

Imagine an online store. A user clicks the "Add to Cart" button — this is a signal for the Controller. The Controller asks the Model to update the data. The Model says: "Done!" The Controller selects the appropriate View and sends it fresh data. The View simply renders what it received.

Here's a minimal C# code example for ASP.NET Core MVC:

// Model\npublic class Product\n{\n    public int Id { get; set; }\n    public string Name { get; set; }\n    public decimal Price { get; set; }\n}\n\n// Controller\npublic class ProductController : Controller\n{\n    private readonly AppDbContext _context;\n\n    public ProductController(AppDbContext context)\n    {\n        _context = context;\n    }\n\n    public IActionResult Index()\n    {\n        var products = _context.Products.ToList();\n        return View(products); // The View itself decides how to render the list\n    }\n}

When to use: web applications with a rich UI where you need to clearly separate logic and presentation. Ideal for C# application architecture on ASP.NET Core.

MVP Pattern: For Those Who Are Friends with Windows Forms

Model-View-Presenter (MVP) is the older brother of MVC, especially good for desktop applications on WinForms or WPF. The main difference: the View is a passive "dummy," and the Presenter manages the entire process.

Example for WinForms

// View Interface (passive)\npublic interface ILoginView\n{\n    string UserName { get; }\n    string Password { get; }\n    event EventHandler LoginClicked;\n    void ShowError(string message);\n}\n\n// Presenter (active conductor)\npublic class LoginPresenter\n{\n    private readonly ILoginView _view;\n    private readonly IAuthService _authService;\n\n    public LoginPresenter(ILoginView view, IAuthService authService)\n    {\n        _view = view;\n        _authService = authService;\n        _view.LoginClicked += OnLoginClicked;\n    }\n\n    private void OnLoginClicked(object sender, EventArgs e)\n    {\n        if (_authService.Authenticate(_view.UserName, _view.Password))\n        {\n            // Navigate to main form\n        }\n        else\n        {\n            _view.ShowError("Invalid username or password");\n        }\n    }\n}

Pro: The View can be easily tested by substituting it with a mock object. Con: There is more code, but it becomes predictable.

Repository Pattern: Hiding Database Complexity

Repository pattern C# is a layer between business logic and the data store. Instead of scattering SQL queries throughout the code, you create a single "repository" for working with entities.

Example with Entity Framework Core

public interface IProductRepository\n{\n    Task<Product> GetByIdAsync(int id);\n    Task<IEnumerable<Product>> GetAllAsync()