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crear-y-configurar-proyecto-aspnet

How to Create a Project in ASP.NET

  • 5 min
  • Beginner

In this article, we are going to see how to create and configure a project in ASP.NET, going through the initial steps that will allow us to start working with the technology.

Logically, it’s the starting point: it doesn’t matter if you’re taking your first steps or preparing to build a real project, the first thing is to create the project 😋.

But also, it will allow us to understand the structure, basic configuration, and operation of an ASP.NET project.

Don’t worry if you’re a bit lost at first. It’s normal, it’s the first project. You’ll get the hang of it quickly.

Prerequisites

Before installing and configuring ASP.NET, make sure you have the following installed on your system:

  1. .NET SDK: It’s the foundation for developing .NET applications.
  2. An IDE or code editor: I recommend using Visual Studio 2022 or Visual Studio Code.
  3. Basic knowledge of C#: It’s not mandatory but… yes, a little bit is needed 😉

If you are missing any of them, take a look at,

Create Your First ASP.NET Core Application

Creating an ASP.NET Core application is simple. We can use tools like Visual Studio or the .NET CLI.

Simply execute a command to create the project, depending on the type we want. For example, to create a new API project

dotnet new webapi -n MiPrimeraApp

Now change to the project directory,

cd MiPrimeraApp

Open Visual Studio and select Create a new project, and search for asp.net.

create-aspnet-app

Accept, and configure the project details.

What This Code Does

When we create our project, it will have a basic structure, with minimal code (so we don’t start from scratch).

Specifically, it’s a very simple API made with ASP.NET that exposes an endpoint (/weatherforecast).

When a user accesses that route, the API returns a JSON with weather information for the next 5 days.

Let’s analyze the code of this base application, because it contains what’s necessary to understand how ASP.NET works.

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

var summaries = new[]
{
    "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
};

app.MapGet("/weatherforecast", () =>
{
    var forecast =  Enumerable.Range(1, 5).Select(index =>
        new WeatherForecast
        (
            DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
            Random.Shared.Next(-20, 55),
            summaries[Random.Shared.Next(summaries.Length)]
        ))
        .ToArray();
    return forecast;
})
.WithName("GetWeatherForecast");

app.Run();

record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
{
    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
}
Copied!
  • ✅ Creates a C# API with ASP.NET Core
  • ✅ Defines a /weatherforecast endpoint that returns a JSON with the weather for the next 5 days
  • ✅ Generates random data (date, temperature, and weather description)
  • ✅ ASP.NET automatically converts the response to JSON

Let’s look at each of these points in detail 👇,

The web application is created:

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();
Copied!
  • builder is the one that configures the application.
  • app is the application ready to run.

The /weatherforecast route is configured

app.MapGet("/weatherforecast", () =>
Copied!
  • This means that if someone makes a GET request to /weatherforecast, the function defined there will be executed.

Each forecast is built using the WeatherForecast class

var forecast =  Enumerable.Range(1, 5).Select(index =>
new WeatherForecast
(
	DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
	Random.Shared.Next(-20, 55),
	summaries[Random.Shared.Next(summaries.Length)]
))
.ToArray();
return forecast;
Copied!
  • The date is today + index days.
  • The temperature is random between -20 and 55 degrees.
  • A random weather summary is chosen.

Everything is converted into an array and returned as a response:**

return forecast;
Copied!
  • Since no return type is specified, by default ASP.NET automatically serializes it to JSON.

ASP.NET Core, by default, uses automatic serialization. When a function returns an object or a list of objects, it converts it to JSON without us having to do anything extra.

Example Response

For example, if we call GET /weatherforecast, the response could be something like this:

[ { “date”: “2025-04-01”, “temperatureC”: 12, “summary”: “Cool”, “temperatureF”: 53 }, { “date”: “2025-04-02”, “temperatureC”: 25, “summary”: “Warm”, “temperatureF”: 77 } ]

  • "date" → Forecast date.
  • "temperatureC" → Temperature in degrees Celsius.
  • "summary" → Weather description.
  • "temperatureF" → It is calculated inside the record WeatherForecast and is returned automatically.

Run

Now you can try to run your application. To do this, you simply have to execute this command from the CLI.

dotnet run

Or press the ▶️ button if you are using Visual Studio.

In either case, you will see an output like the following.

aspnet-run

Now you can access from your browser (Chrome, Firefox, etc…) to this address,

localhost:5288/weatherforecast

And you will see ASP.NET’s response, with the weather forecast data (made up of course, it’s an example), in JSON format.

aspnet-weatherforecast

That’s how easy it is! It’s not much more complicated to launch an API with ASP.NET. Now you can continue reading the rest of the course to master this technology 😉.

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