ASP.NET Core is one of the most popular open-source web frameworks for building modern web applications and services on the .NET platform. Its modular and lightweight design, cross-platform support, high performance, and rich ecosystem make it a great choice for building web APIs, websites, mobile backends, and more.

In this beginner-friendly tutorial, we'll build a simple "Hello World" ASP.NET Core web application from scratch. We'll walk through:

• Setting up the development environment with the .NET Core SDK
• Creating a new ASP.NET Core project
• Running the app locally
• Adding a basic web API endpoint
• Testing the output

By the end, you'll have a good foundational understanding of how ASP.NET Core works and be ready to build more complex real-world applications. The goal is to get you up and running with core concepts so you can start leveraging the power and capabilities of ASP.NET Core for your own projects.

Let's get started!

Prerequisites

Before we start, make sure you have the following installed:

• .NET Core SDK 3.1 or later
• A text editor or IDE like Visual Studio, Visual Studio Code etc.

Create the Application

Let's start by creating a new ASP.NET Core web application.

• Open a command prompt or terminal and navigate to the directory where you want to create the app.

• Type the following command:
  

dotnet new web -o MyFirstApp

It will create a new ASP.NET Core web project in a folder called MyFirstApp.

• Navigate into this new folder:

cd MyFirstApp

The project contains a Program.cs file with the entry point code and a Startup.cs file for configuring services and the request pipeline.

Run the Application

We can now run the web app locally to see the default page.

• From the command prompt in the application folder, run:

dotnet run

Open a web browser and go to https://localhost:5001. You should see the default ASP.NET Core web page.

Add Some Code

Let's add a simple API endpoint to return "Hello World".

• Open the Startup.cs file.
• Add the following code inside the Configure method:

app.Run(async context => 
{
   await context.Response.WriteAsync("Hello World!"); 
});

• Run dotnet run again and refresh the browser. You should now see "Hello World!"

And that's it! We now have a simple ASP.NET Core web application up and running.

Next Steps

This was just a basic example to get started. From here, you can start adding controllers, views, models etc., to build a real web application.

The official ASP.NET Core docs are a great next resource to learn more about ASP.NET Core and its features.

We walked through setting up the development environment, creating a new project, running the application locally, adding a basic API endpoint, and testing the output. This should give ASP.NET Core developers a good overview of the basic structure and workflow of ASP.NET Core applications. Of course, this was just a simple example - ASP.NET Core is capable of powering robust, scalable enterprise web applications and services. The official documentation contains many more in-depth guides on leveraging the full capabilities of ASP.NET Core.

I hope this tutorial served as an easy way for ASP.NET Core developers to get started building web applications on the .NET platform. Let me know if you have any other questions!