Understanding ASP.NET Core Project Structure

ASP.NET Core follows a structured and modular approach. Let's break down the key components of a typical ASP.NET Core project.

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🔹 1️⃣ Project Structure Overview

📂 MyAspNetApp/
├── 📄 Program.cs ➝ Application Entry Point
├── 📄 appsettings.json ➝ Configuration Settings
├── 📂 wwwroot/ ➝ Static Files (CSS, JS, Images)
├── 📂 Controllers/ ➝ Handles HTTP Requests (MVC API)
├── 📂 Models/ ➝ Defines Data Structures
├── 📂 Views/ ➝ Handles UI Rendering (Razor Views for MVC)
├── 📂 Middleware/ ➝ Custom Request Processing Logic

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🔹 2️⃣ Program.cs - Application Entry Point

• This is where the ASP.NET Core app starts.
• It registers services, configures middleware, and sets up the request pipeline.

Example Program.cs File:

var builder = WebApplication.CreateBuilder(args);

// Add services to the container
builder.Services.AddControllersWithViews();  // Enables MVC

var app = builder.Build();

// Configure Middleware Pipeline
app.UseStaticFiles();  // Serve static files (CSS, JS, Images)
app.UseRouting();      // Enables routing
app.UseAuthorization(); // Enables authentication

// Define Routes
app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}"
);

app.Run();

Key Takeaways:

• builder.Services.AddControllersWithViews(); ➝ Adds MVC functionality.
• app.UseRouting(); ➝ Enables routing for controllers.
• app.UseAuthorization(); ➝ Enables security/authentication.
• app.MapControllerRoute(); ➝ Defines the default route (Controller, Action, ID).

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🔹 3️⃣ Controllers (Handles HTTP Requests)

📂 Controllers/
├── HomeController.cs

Controllers handle requests and return responses (JSON, Views, etc.).

Example Controller (HomeController.cs)

using Microsoft.AspNetCore.Mvc;

public class HomeController : Controller
{
    public IActionResult Index()
    {
        return View();  // Renders the corresponding View (Index.cshtml)
    }

    public IActionResult About()
    {
        return Content("About Page");
    }
}

Key Takeaways:

• Index() ➝ Loads a View (Views/Home/Index.cshtml)
• About() ➝ Returns plain text (Content())

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🔹 4️⃣ Models (Data Handling Layer)

📂 Models/
├── Product.cs

Models define data structures and are used to transfer data between controllers and views.

Example Model (Product.cs)

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

Key Takeaways:

• Models represent data entities (e.g., Product, User, Order).
• Used for data validation and business logic.

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🔹 5️⃣ Views (UI Layer for MVC Applications)

📂 Views/
├── Home/
│   ├── Index.cshtml
│   ├── About.cshtml

Views define the HTML UI for the application using Razor syntax (.cshtml).

Example View (Index.cshtml)

@{
    ViewData["Title"] = "Home Page";
}

<h1>Welcome to ASP.NET Core!</h1>
<p>This is the home page.</p>

Key Takeaways:

• Uses Razor syntax (@{} for C# code).
• Dynamically renders data in MVC applications.

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🔹 6️⃣ Middleware (Custom Request Processing Logic)

📂 Middleware/
├── CustomMiddleware.cs

Middleware intercepts HTTP requests and processes them before reaching the controller.

Example Custom Middleware (CustomMiddleware.cs)

public class CustomMiddleware
{
    private readonly RequestDelegate _next;

    public CustomMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        Console.WriteLine($"Request Path: {context.Request.Path}");
        await _next(context);
    }
}

To use this middleware, register it in Program.cs:

app.UseMiddleware<CustomMiddleware>();

Key Takeaways:

• Middleware runs before controllers process the request.
• Used for logging, authentication, exception handling, etc.

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🔹 7️⃣ Default Routing in ASP.NET Core

ASP.NET Core uses convention-based routing by default:

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}"
);

This means:

• http://localhost:5000/ ➝ Calls HomeController.Index()
• http://localhost:5000/Home/About ➝ Calls HomeController.About()

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✅ Summary

Component	Purpose
Program.cs	Application entry point, registers services & middleware
Controllers/	Handles HTTP requests and returns data/views
Models/	Defines data structures and business logic
Views/	Handles UI rendering (for MVC apps)
Middleware/	Custom logic that runs before controllers
wwwroot/	Static files like CSS, JS, Images

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