MSDN Documentation

Introduction to ASP.NET

ASP.NET is a free, open-source, cross-platform framework for building modern, cloud-based, internet-connected applications. It can be used to build web applications, services, and components.

With ASP.NET, you can build applications that:

  • Run on Windows, macOS, and Linux.
  • Are cross-platform compatible.
  • Are developed using C#, F#, or Visual Basic.
  • Are open-source and community-driven.

Core Concepts

Understanding the core concepts of ASP.NET is crucial for building robust web applications. These include:

  • Server-side logic: ASP.NET executes code on the server to generate dynamic content.
  • HTML, CSS, JavaScript: These client-side technologies are used to build the user interface.
  • Request/Response Cycle: The fundamental mechanism by which clients and servers communicate.
  • Web Server: Typically IIS on Windows, or Kestrel on cross-platform environments.

Architecture Overview

ASP.NET provides a flexible architecture that supports various development models:

  • ASP.NET Core: The modern, high-performance, cross-platform evolution of ASP.NET.
  • Razor Pages: A page-centric programming model for building web UIs with ASP.NET Core.
  • Model-View-Controller (MVC): A popular pattern for building well-structured, testable applications.
  • Web API: For building HTTP services that can be consumed by a wide range of clients.

Request Lifecycle

Every incoming HTTP request goes through a defined lifecycle:

  1. Request received by the web server.
  2. Request is routed to the ASP.NET application.
  3. Middleware pipeline processes the request.
  4. Application logic is executed (e.g., controller action, Razor Page handler).
  5. Response is generated.
  6. Response is sent back to the client.

The middleware pipeline is a powerful feature that allows you to add custom logic for handling requests and responses, such as authentication, logging, and error handling.

MVC Pattern

The Model-View-Controller (MVC) architectural pattern separates an application into three interconnected components:

  • Model: Represents the application's data and business logic.
  • View: Responsible for displaying data to the user (usually HTML, CSS, and JavaScript).
  • Controller: Handles user input, interacts with the Model, and selects the appropriate View to render.

This separation promotes cleaner code, better organization, and improved testability.

Razor Pages

Razor Pages offer a simpler, page-focused programming model that makes it easy to build dynamic web UIs. It's well-suited for scenarios where:

  • You want a more streamlined approach than MVC.
  • You have a page-centric application with minimal complex business logic.
  • You are familiar with server-side Razor syntax.

A Razor Page typically consists of a .cshtml file for the UI markup and a corresponding .cshtml.cs file for the page-specific code-behind logic.

Web API

ASP.NET Web API is a framework for building HTTP services. It allows you to expose data and functionality to various clients, including browsers, mobile apps, and other services.

Key features of Web API include:

  • Support for common HTTP methods (GET, POST, PUT, DELETE).
  • Content negotiation for various data formats (JSON, XML).
  • Routing based on URL and HTTP method.
  • Built-in support for model binding and validation.

Example of a simple API controller:


using Microsoft.AspNetCore.Mvc;

[ApiController]
[Route("api/[controller]")]
public class ProductsController : ControllerBase
{
    [HttpGet]
    public IEnumerable<string> Get()
    {
        return new string[] { "Product 1", "Product 2" };
    }
}

Authentication & Authorization

Securely managing user access is paramount. ASP.NET provides robust mechanisms for:

  • Authentication: Verifying the identity of a user. This can involve cookies, JWT tokens, OAuth, OpenID Connect, and more.
  • Authorization: Determining what an authenticated user is allowed to do. This can be role-based, policy-based, or resource-based.

ASP.NET Core Identity is a comprehensive membership system that handles user registration, login, password management, and roles.

State Management

Web applications are often stateless, meaning each request is independent. To maintain user context and data across requests, ASP.NET offers various state management techniques:

  • Cookies: Small pieces of data stored on the client's browser.
  • Session State: Server-side storage of user-specific data for the duration of their visit.
  • Application State: Data accessible to all users of the application.
  • View State: (Primarily in older ASP.NET Web Forms) Data persisted on the client-side within hidden form fields.
  • Local Storage / Session Storage: Client-side storage APIs available in modern browsers.

Deployment

Deploying ASP.NET applications involves packaging your application and hosting it on a web server.

Key considerations include:

  • Publishing: Creating a deployable artifact of your application.
  • Hosting Environment: Choosing between on-premises servers, cloud platforms (Azure, AWS, GCP), or containerization (Docker).
  • Web Server Configuration: Setting up IIS, Kestrel, or other web servers.
  • Database Deployment: Ensuring your data store is accessible and configured correctly.

Continuous Integration and Continuous Deployment (CI/CD) pipelines are highly recommended for streamlining the deployment process.