To follow the directions in this chapter, you’ll need to have the following installed on your Windows, macOS, or Linux machine:

• .NET 9.0 Software Development Kit (SDK)
• Visual Studio or Visual Studio Code
• C# extension for Visual Studio Code (if you are using Visual Studio Code)

If you’re working in Windows, it’s recommended that you use Visual Studio, although Visual Studio Code will still work. If you’re a Mac or Linux user, you should use Visual Studio Code. (At the time of writing, Visual Studio for Mac is set to be retired on August 31, 2024.)

The code for this chapter is available in the GitHub repository at: https://github.com/PacktPublishing/Minimal-APIs-in-ASP.NET-9.

When it comes to designing and building APIs, we’re spoilt for choice with varying styles, approaches, and templates. .NET has proven itself over the years to be a fantastic choice for general-purpose API development. Modern .NET provides us with two main types of API framework, one more traditional than the other. One of the options is, of course, the minimal API, which is still a relatively new feature within .NET compared to its predecessor, the controller-based API.

With minimal APIs, the aim is simplicity. Less code, less ceremony, and less complexity. As a result, minimal APIs are well suited to microservice architectures, where you have lots of small components all requiring a means of transferring data between each other.

Their simplicity also makes them easier to read, as a small block of code can take care of all the classic features of an API, such as receiving HTTP requests, routing, utilizing dependencies, accessing services, and...

The more traditional API format in .NET compared to minimal APIs is controller-based APIs. These are more commonly seen in ASP.NET Model-View-Controller (MVC) projects, or in ASP.NET web API projects. However, whether you’re building an MVC project or not, both API types utilize controllers.

Controllers are simply classes, with many responsibilities within the API, such as the following:

• Handling incoming requests via actions, which are interacted with using various HTTP methods, such as GET, POST, PUT, DELETE, and PATCH.
• Processing data sent in the request via query string parameters or within the request body.
• Interaction with data models and processing of business logic via services.
• Generation of responses to calling clients. These responses could be in JSON, XML, or many other formats.

  Routing of requests to other areas of the application, that is, directing to a page at a specific URL.

The concept of creating more lightweight and simple APIs has been around for some time, but the adoption of minimal APIs has increased over the years. Flask and Express.js have historically promoted some elements of minimalism in API development within Python and Node.js, respectively, but compared to its counterparts, .NET’s recent entry into the market is specifically designed to exploit the advantages of lightweight, simple APIs.

Now that minimal APIs have arrived and are being used in mainstream development projects, developers are enjoying the benefits of not having to perform lots of setup and configuration. They can have a working API up and running in two minutes and deploy it to the cloud in another two. This provides phenomenal advantages for industries in which getting software to market quickly is critical to success.

In addition, the APIs you write can take advantage of .NET’s mature, cross-platform...

For us to begin working with minimal APIs, we need to install some tools.

Let us start by installing the .NET 9.0 SDK. Navigate to Microsoft’s .NET SDK downloads page at https://dotnet.microsoft.com/en-us/download/dotnet. (This can be skipped if you already have the SDK installed.)

At the time of writing, the SDK is available by doing the following:

1. Choose the appropriate build for your operating system and system architecture. For example, if you are running 64-bit Windows, you would download x64. Likewise, if you were running a Mac with an ARM CPU, you would select Arm64 next to macOS. Linux tends to be a little different because a package manager is used to obtain the SDK.

   If you are a Linux user, follow the relevant Microsoft documentation for your specific Linux distribution:

Figure 1.1: Choosing the right installer

Before we move on, let us quickly differentiate between installers...

We’ll start to develop our first minimal API in the next chapter, but before that, let’s create the project structure needed for us to start writing code.

To build minimal APIs, we need to be working within an ASP.NET Core project. Depending on whether you are using Visual Studio or Visual Studio Code, there are several ways you can create this type of project.

Creating a project in Visual Studio

Let’s begin by creating a project in Visual Studio:

1. Open Visual Studio.
2. The screen shown in the following figure gives you the option to search for the type of project you wish to create. Search for ASP.NET Core Empty and select it from the list, before clicking Next. (Make sure you choose the C# version of the template. Do not use the F# version, as this is not within the scope of this book.)

Figure 1.5: Visual Studio’s new project creation screen

3. Give your new project...

In this chapter, you learned about the role of minimal APIs in modern application development, and you should now have a good general understanding of their advantages.

You learned how minimal APIs differ from controller-based APIs in .NET, and gained an understanding of the advantages and disadvantages of these two formats.

You installed the basic required libraries and tools to get started on your journey and learned how to create a new project in Visual Studio or Visual Studio Code.

The key takeaway from this chapter is that minimal APIs promote simplicity, high performance, and maintainability.

In the next chapter, we will start writing our first Minimal API endpoints, which will be able to handle various HTTP methods on different routes. We will minimal build responses to send back to clients and make calls to our API.