Steve Fenton

Just a quick note on a neat feature in C# 9 that will allow sub-classes to return a covariant return type… what?! Okay, it allows you to return a more specific, or narrower type. For example, we used to have to return the same type… // parent class… public virtual Literature GetLiterature(…) { return new […]

This neat C# 9 feature can be summed up in a tiny snippet of code. You know that code analysis warning that tells you that the argument passed might be null… wouldn’t it be nice if you could refuse to accept null? Well, you can. This is the before… public Book(string firstName, string lastName) And […]

Update! Since this article was published, it is almost certain that the keyword for record types will actually be record not data as it was in this early preview. We have taken a quick look at C# 9 Initializers and Immutability and C# 9 Non-Destructive Mutation. Let’s now look at the full transformation from an […]

There are some phrases in programming that feel like they belong in a superhero movie. Non-destructive mutation is just such as phrase. It refers to a concept in functional programming that means when you want to change the state of an object, you create a copy with the change – rather than changing the original. […]

There is currently a compromise in C# that means you can enable object initialization with getters and setters, or you can prevent external code mutating state by hiding the setter… but not both. C# 9 gives us both with the init keyword. Let’s look at before… public class Book { public string Author { get; […]

At Microsoft Build 2020, an interesting new “see less boilerplate” feature from C# 9 was demonstrated. It removes all the code to create the class and static Main method, letting you just start typing your code. It makes your code way-less-nested (okay, two levels), but doesn’t miss any of your usual features. For example, args […]