ASP.NET Core for Beginners: Build Your First Web Application

ASP.NET Core is the web framework in .NET for building websites, web APIs, real-time applications, and backend services. It gives you a hosting model, routing, middleware, dependency injection, configuration, and several ways to build HTTP applications.

Create a project

In Visual Studio, choose an ASP.NET Core template, or create a small Razor Pages application from a terminal:

dotnet new webapp -n MyFirstWebApp
cd MyFirstWebApp
dotnet run

The template creates the project files and a simple application that you can run locally.

What happens when you run it?

The application starts an ASP.NET Core host and listens on a local HTTP or HTTPS address. The terminal or Visual Studio output shows the addresses being used. Open one of them in a browser to view the application.

Pages, controllers, and APIs

ASP.NET Core supports several application styles. Razor Pages are useful for page-focused applications. MVC uses controllers and views to separate request handling and presentation. Web APIs expose HTTP endpoints for clients, while minimal APIs provide a lightweight way to define endpoints in code.

Middleware

Middleware components participate in processing an HTTP request and response. Authentication, exception handling, static files, routing, and logging are common examples. The order in which middleware is added can affect application behavior.

Dependency injection

ASP.NET Core includes dependency injection by default. Instead of constructing every service inside a controller or page, you can register services with the application and ask for them where they are needed. This improves separation of responsibilities and testability.

Configuration

ASP.NET Core can read configuration from sources such as JSON configuration files, environment variables, and command-line arguments. Keep secrets out of source control and use appropriate secret-management mechanisms for deployment.

Common beginner mistakes

Trying to open the application at the wrong port shown during startup.
Adding middleware in an order that prevents routing, authentication, or endpoint handling from working as intended.
Putting production secrets directly into a checked-in configuration file.

Next step

Continue with the ASP.NET Core Tutorials pillar for dependency injection, validation, middleware, authentication, APIs, and SignalR.

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