Use the power of Source Generators with Lombok.NET

Since the introduction of source generators in .NET 5, I always wondered what the cool use cases would be that this feature makes possible. Today I want to introduce to you Lombok.NET, as an example of what Source Generators make possible.

Lombok.NET

If you are a Java developer, the name ‘Lombok’ maybe rings a bell. Lombok.NET is inspired by Project Lombok, a Java library with as main goal to help you minimize the amount of boilerplate code you need to write. I have no clue how this exactly works in Java, but Lombok.NET has the same goal using Source Generators.

Here are the list of features that Lombok.NET supports today:

• Constructors
• "With" methods
• Singletons
• Lazy
• INotifyPropertyChanged/INotifyPropertyChanging
• Async overloads
• ToString
• Decorator pattern

Let’s have a look at 2 of them that I use the most.

Installation

Before we can use Lombok.NET, we need to install it first. this is quite easy because it is just a NuGet package:

dotnet add package Lombok.NET

Usage

Now we start using Lombok.NET. The way that it works is by annotating our classes, structs, interfaces, … with some attributes.

ToString

The first one I want to show you is the [ToString] attribute.  This will generate a ToString implementation that will print out all the private fields(can be configured) from your class.

We start with a Person class with 2 properties. Notice that I made the class partial. This is required so that Lombok.NET can extend the class definition without having to update the original file.

	public partial class Person
	{
	public string Name { get; set; }
	public int Age { get; set; }
	}

view raw Person.cs hosted with ❤ by GitHub

Now we introduce the [ToString] attribute. I set the MemberType to MemberType.Property and  AccessTypes to AccessTypes.Public because I want to include the public properties in the generated ToString implementation:

	[ToString(MemberType = MemberType.Property, AccessTypes = AccessTypes.Public)]
	public partial class Person
	{
	public string Name { get; set; }
	public int Age { get; set; }
	}

view raw Person.cs hosted with ❤ by GitHub

If we now build our code, a partial class is generated:

Let’s have a look at what is inside:

	public partial class Person
	{
	public override string ToString()
	{
	return $"Person: Name={Name}; Age={Age}";
	}
	}

view raw Person.partial.cs hosted with ❤ by GitHub

Nice!

Async Overloads

Let’s have a look at another example. With Async Overloads Lombok.NET will generate an async overload for every method in your interface(it also works for abstract classes and methods).

Here is an example of a small IRepository interface. Notice that here as well I need to make the interface partial:

	public partial interface IRepository<T>
	{
	T GetById(int id);
	IEnumerable<T> GetAll();
	}

view raw IRepository.cs hosted with ❤ by GitHub

We add an [AsyncOverloads] attribute to annotate our interface:

	[AsyncOverloads]
	public partial interface IRepository<T>
	{
	T GetById(int id);
	IEnumerable<T> GetAll();
	}

view raw IRepository.cs hosted with ❤ by GitHub

If we build our code, a partial interface is generated . Here is what is inside:

	public partial interface IRepository<T>
	{
	global::System.Threading.Tasks.Task<T> GetByIdAsync(int id, global::System.Threading.CancellationToken cancellationToken = default);
	global::System.Threading.Tasks.Task<IEnumerable<T>> GetAllAsync(global::System.Threading.CancellationToken cancellationToken = default);
	}

view raw IRepository.partial.cs hosted with ❤ by GitHub

Certainly have a look at the other possibilities that Lombok.NET has to offer.

And if you are looking at some other use cases where Source Generators are useful, here are some examples:

• Introduction to MVVM Source Generators for C# .NET (hashnode.dev)
• Optimize your API performance with the System.Text.Json source generator (bartwullems.blogspot.com)
• .NET regular expression source generators | Microsoft Learn
• Compile-time logging source generation - .NET | Microsoft Learn