Session 6.5 – Introduction to ASP.NET

Introduction to ASP.NET

ASP.NET is a free, cross-platform, open-source framework for building modern web applications and services with .NET. It's maintained by Microsoft and the .NET community.

What is ASP.NET?

Framework: Built on the .NET platform
Language: Primarily C#, also supports VB.NET and F#
Platform: Cross-platform (Windows, macOS, Linux)
Architecture: Supports MVC, Web API, Blazor, and more
Performance: Known for excellent performance and scalability

ASP.NET Core MVC

Modern MVC framework for web applications and APIs

ASP.NET Web API

RESTful API framework for HTTP services

Blazor

Build interactive web UIs using C# instead of JavaScript

ASP.NET Framework Overview

.NET Architecture

Application Layer

ASP.NET Core MVC | Web API | Blazor | Razor Pages

Framework Layer

.NET Core Runtime | ASP.NET Core Libraries

Base Class Library

Collections | I/O | Networking | Security | Threading

Key Features

High Performance

ASP.NET Core is one of the fastest web frameworks, with excellent request throughput and low latency.

Cross-Platform

Develop and deploy on Windows, macOS, and Linux. Host in IIS, Apache, Docker, or self-host.

Modular Design

Include only the packages you need via NuGet. Reduces application footprint and improves security.

Dependency Injection

Built-in dependency injection support promotes loose coupling and testability.

MVC Pattern in ASP.NET

MVC Architecture

Model

Data structures
Business logic
Database operations
Data validation

View

User interface
Presentation logic
Razor templates
Display data

Controller

Handles requests
Processes input
Updates models
Selects views

Controller Example

using Microsoft.AspNetCore.Mvc;
using MyApp.Models;

namespace MyApp.Controllers
{
    public class HomeController : Controller
    {
        // GET: /Home/Index
        public IActionResult Index()
        {
            return View();
        }

        // GET: /Home/About
        public IActionResult About()
        {
            ViewData["Message"] = "Your application description page.";
            return View();
        }

        // GET: /Home/User/5
        public IActionResult User(int id)
        {
            var user = GetUserById(id);
            if (user == null)
            {
                return NotFound();
            }
            return View(user);
        }

        // POST: /Home/Create
        [HttpPost]
        public IActionResult Create(User user)
        {
            if (ModelState.IsValid)
            {
                // Save to database
                SaveUser(user);
                return RedirectToAction("Index");
            }
            return View(user);
        }
    }
}

Model Example

using System.ComponentModel.DataAnnotations;

namespace MyApp.Models
{
    public class User
    {
        public int Id { get; set; }

        [Required(ErrorMessage = "Name is required")]
        [StringLength(100)]
        public string Name { get; set; }

        [Required]
        [EmailAddress]
        public string Email { get; set; }

        [Range(18, 120)]
        public int Age { get; set; }

        [DataType(DataType.Password)]
        public string Password { get; set; }

        [Display(Name = "Registration Date")]
        public DateTime RegisteredAt { get; set; }
    }
}

Razor Syntax

Razor is a markup syntax for embedding server-based code into web pages. It uses the @ symbol to transition from HTML to C#.

Basic Razor Syntax

@* This is a Razor comment *@

<!-- Display variable -->
<p>Hello, @Model.Name!</p>

<!-- Code block -->
@{
    var message = "Welcome to ASP.NET";
    var currentYear = DateTime.Now.Year;
}

<h1>@message</h1>
<p>Copyright © @currentYear</p>

<!-- Conditional rendering -->
@if (Model.IsLoggedIn)
{
    <p>Welcome back, @Model.Username!</p>
}
else
{
    <p><a href="/login">Please log in</a></p>
}

<!-- Loop -->
<ul>
    @foreach (var item in Model.Items)
    {
        <li>@item.Name - $@item.Price</li>
    }
</ul>

View Example (Index.cshtml)

@model IEnumerable<MyApp.Models.User>

@{
    ViewData["Title"] = "User List";
}

<h2>@ViewData["Title"]</h2>

<p>
    <a asp-action="Create" class="btn btn-primary">Create New User</a>
</p>

<table class="table table-striped">
    <thead>
        <tr>
            <th>@Html.DisplayNameFor(model => model.Name)</th>
            <th>@Html.DisplayNameFor(model => model.Email)</th>
            <th>@Html.DisplayNameFor(model => model.Age)</th>
            <th>Actions</th>
        </tr>
    </thead>
    <tbody>
        @foreach (var user in Model)
        {
            <tr>
                <td>@user.Name</td>
                <td>@user.Email</td>
                <td>@user.Age</td>
                <td>
                    <a asp-action="Edit" asp-route-id="@user.Id">Edit</a> |
                    <a asp-action="Details" asp-route-id="@user.Id">Details</a> |
                    <a asp-action="Delete" asp-route-id="@user.Id">Delete</a>
                </td>
            </tr>
        }
    </tbody>
</table>

Form Example

@model MyApp.Models.User

<h2>Create User</h2>

<form asp-action="Create" method="post">
    <div asp-validation-summary="ModelOnly" class="text-danger"></div>

    <div class="form-group">
        <label asp-for="Name" class="control-label"></label>
        <input asp-for="Name" class="form-control" />
        <span asp-validation-for="Name" class="text-danger"></span>
    </div>

    <div class="form-group">
        <label asp-for="Email" class="control-label"></label>
        <input asp-for="Email" class="form-control" />
        <span asp-validation-for="Email" class="text-danger"></span>
    </div>

    <div class="form-group">
        <label asp-for="Age" class="control-label"></label>
        <input asp-for="Age" class="form-control" />
        <span asp-validation-for="Age" class="text-danger"></span>
    </div>

    <div class="form-group">
        <input type="submit" value="Create" class="btn btn-primary" />
        <a asp-action="Index" class="btn btn-secondary">Cancel</a>
    </div>
</form>

@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}

ASP.NET vs PHP

ASP.NET

Advantages:

Strong typing and compile-time checking
Excellent IDE support (Visual Studio)
Built-in dependency injection
High performance
Enterprise-grade features
Great for large-scale applications

Considerations:

Steeper learning curve
Less hosting options than PHP
Traditionally Windows-centric (changing)

PHP