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Showing posts from September, 2021

Type aliases using C# Source Generators and C# 10 generic attributes

When practicing domain-driven design, a reoccurring chore is the creation of value types. These are strongly typed representations of simple types like strings that have a specific meaning, like CustomerId or ProductCode. These could both be strings but we put preferably implement them as strongly typed variations so that we can't for instance mix up multiple string parameters while coding. In some languages, this is something that comes out of the box and is often referred to as type aliasing. C# does not support this. Although in C# you could give another name to a string type with a using statement, it still remains a string (the type does not change).  This task is so common and tedious that it makes it the perfect case for implementing a source generator. Creating a type alias should be as simple as adding an attribute indicating what type should be aliased. It should also work for all kinds of types, like class, record, struct, and record struct. The full source code can be f

Simple but effective use of C# Source Generators

Most C# source generator examples I have encountered included more advanced features like augmenting existing classes with generated code. There are much simpler scenarios where they are useful though. For instance, just avoiding typing repetitive code. For the full source code, consult my GitHub repo here . Imagine writing a number of overloads where only the function name changes. In this case, I want to create HTML tags as strings using a function. The example is a set of overloads for the anchor ('a') tag: public static Node a(params Node[] nodes) =>      element(nameof(a), Array.Empty<IAttribute>(), nodes); public static Node a(params IAttribute[] attributes) =>      element(nameof(a), attributes, Array.Empty<Node>()); public static Node a(IEnumerable<IAttribute> attributes, params Node[] children) =>      element(nameof(a), attributes, children); Now I want the have the same overloads for all HTML tags. That's a lot of repetition. To cre