"Init-Only Setters"

public class User {
	public string Name { get; init; }
	public int Age { get; init; }
}

// ...

var user = new User { Name = "Ben", Age = 30 };
user.Name = "Seb"; // Won't compile, 'Name' is init-only


Code snippet taken from "Two Decades of C#: A Reference - C# 9".