An Introduction to ASP.NET Core

For many years, ASP.NET was a powerful but Windows-only framework for building web applications. That all changed with the introduction of ASP.NET Core. ASP.NET Core is a complete redesign of the original framework, built from the ground up to be open-source, cross-platform, and high-performance.

It's the modern way to build web applications, APIs, and microservices with .NET, and it can run on Windows, macOS, and Linux.

Key Features of ASP.NET Core

What makes ASP.NET Core a great choice for modern web development?

1. Cross-Platform

This is the biggest change from the old ASP.NET. You can develop and run your ASP.NET Core applications anywhere. This opens up a huge range of possibilities, from developing on a Mac to deploying your application in a Linux-based Docker container.

2. High Performance

Performance is a top priority for the ASP.NET Core team. The framework is consistently ranked as one of the fastest mainstream web frameworks in the TechEmpower benchmarks, often outperforming frameworks like Node.js and Go.

3. Unified Framework for Web UI and Web APIs

ASP.NET Core provides a single, unified framework for building both web UIs (using technologies like Razor Pages or MVC) and web APIs. This provides a consistent development experience across your application.

4. Built-in Dependency Injection

ASP.NET Core includes a simple but powerful built-in dependency injection (DI) container. DI is a design pattern that helps you build loosely coupled, more testable, and more maintainable applications. It's a first-class citizen in ASP.NET Core, and the framework itself uses it extensively.

5. Middleware Pipeline

In ASP.NET Core, the HTTP request pipeline is composed of a series of middleware components. Each piece of middleware is a component that can inspect, modify, or handle an incoming request. This gives you fine-grained control over how requests are processed. Common middleware includes authentication, routing, and static file serving.

6. Open-Source and Community-Focused

The entire ASP.NET Core framework is open-source and developed on GitHub. This transparency allows the community to contribute to the framework and provides insight into the future direction of the platform.

The Startup.cs File

The heart of an ASP.NET Core application is the Startup.cs file. This is where you configure your application's services and its request pipeline.

public class Startup
{
    // This method is where you register services with the DI container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc();
    }

    // This method is where you configure the middleware pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseStaticFiles();
        app.UseMvc();
    }
}

Application Models

ASP.NET Core supports several different models for building web applications:

• ASP.NET Core MVC: A powerful pattern for building web applications and APIs, separating concerns into Models, Views, and Controllers.
• ASP.NET Core Razor Pages: A newer, page-centric model that is often simpler for building simple web UIs. In Razor Pages, the UI logic and the page markup live together in a single file.
• ASP.NET Core Web API: For creating rich RESTful APIs that can be consumed by a wide range of clients.

Conclusion

ASP.NET Core is a modern, fast, and flexible framework for building web applications. Its cross-platform and open-source nature, combined with its focus on performance and developer productivity, has made it a top-tier choice for web development. Whether you are a seasoned .NET developer or new to the ecosystem, ASP.NET Core provides all the tools you need to build powerful, cloud-ready web applications and services.