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Introduction to ASP.NET Core
Get an introduction to ASP.NET Core, a cross-platform, high-performance, open-source framework for building modern, cloud-based, Internet-connected applications.

Introduction to ASP.NET Core

By Daniel Roth, Rick Anderson, and Shaun Luttin

ASP.NET Core is a cross-platform, high-performance, open-source framework for building modern, cloud-based, Internet-connected applications. With ASP.NET Core, you can:

  • Build web apps and services, IoT apps, and mobile backends.
  • Use your favorite development tools on Windows, macOS, and Linux.
  • Deploy to the cloud or on-premises.
  • Run on .NET Core or .NET Framework.

Why use ASP.NET Core?

Millions of developers have used (and continue to use) ASP.NET 4.x to create web apps. ASP.NET Core is a redesign of ASP.NET 4.x, with architectural changes that result in a leaner, more modular framework.

ASP.NET Core provides the following benefits:

  • A unified story for building web UI and web APIs.
  • Integration of modern, client-side frameworks and development workflows.
  • A cloud-ready, environment-based configuration system.
  • Built-in dependency injection.
  • A lightweight, high-performance, and modular HTTP request pipeline.
  • Ability to host on IIS, Nginx, Apache, Docker, or self-host in your own process.
  • Side-by-side app versioning when targeting .NET Core.
  • Tooling that simplifies modern web development.
  • Ability to build and run on Windows, macOS, and Linux.
  • Open-source and community-focused.

ASP.NET Core ships entirely as NuGet packages. Using NuGet packages allows you to optimize your app to include only the necessary dependencies. In fact, ASP.NET Core 2.x apps targeting .NET Core only require a single NuGet package. The benefits of a smaller app surface area include tighter security, reduced servicing, and improved performance.

Build web APIs and web UI using ASP.NET Core MVC

ASP.NET Core MVC provides features to build web APIs and web apps:

  • The Model-View-Controller (MVC) pattern helps make your web APIs and web apps testable.
  • Razor Pages (new in ASP.NET Core 2.0) is a page-based programming model that makes building web UI easier and more productive.
  • Razor markup provides a productive syntax for Razor Pages and MVC views.
  • Tag Helpers enable server-side code to participate in creating and rendering HTML elements in Razor files.
  • Built-in support for multiple data formats and content negotiation lets your web APIs reach a broad range of clients, including browsers and mobile devices.
  • Model binding automatically maps data from HTTP requests to action method parameters.
  • Model validation automatically performs client-side and server-side validation.

Client-side development

ASP.NET Core integrates seamlessly with popular client-side frameworks and libraries, including Angular, React, and Bootstrap. For more information, see Client-side development.

ASP.NET Core targeting .NET Framework

ASP.NET Core can target .NET Core or .NET Framework. ASP.NET Core apps targeting .NET Framework aren't cross-platform—they run on Windows only. There are no plans to remove support for targeting .NET Framework in ASP.NET Core. Generally, ASP.NET Core is made up of .NET Standard libraries. Apps written with .NET Standard 2.0 run anywhere that .NET Standard 2.0 is supported.

There are several advantages to targeting .NET Core, and these advantages increase with each release. Some advantages of .NET Core over .NET Framework include:

  • Cross-platform. Runs on macOS, Linux, and Windows.
  • Improved performance
  • Side-by-side versioning
  • New APIs
  • Open source

We're working hard to close the API gap from .NET Framework to .NET Core. The Windows Compatibility Pack made thousands of Windows-only APIs available in .NET Core. These APIs weren't available in .NET Core 1.x.

Next steps

For more information, see the following resources:

  • Get started with Razor Pages
  • ASP.NET Core tutorials
  • xref:tutorials/publish-to-azure-webapp-using-vs
  • ASP.NET Core fundamentals
  • The weekly ASP.NET community standup covers the team's progress and plans. It features new blogs and third-party software.