Quite recently a colleague of mine did something like this in the codebase:

_ = services

And since I couldn’t find a definition of _ I asked my rubber ducky. What is this? Why is it so badly named? I thought I will never find it using Google. Thank God I did.

All the information I present here can be found inside the linked article above and this blog post should be considered a documentation of my learning process.

So here’s the beginner’s guide to discards in 6 fancy points :-)

1. It is a void for unwanted values

It’s called a discard and it can be defined as:

temporary
dummy variables
that do not have a value
that reduce memory allocations (a single discard variable that may not even be allocated storage)
and it’s intentionally unused in application code
and because they make the intent of your code clear, they enhance its readability and maintainability.

Source

2. You can replace it with a variable scope wise

3. Use it to decompose a tuple

(_, _, area) = city.GetCityInformation(cityName);

4. My personal favorite: Use it when checking parsing results without the need of declaring new variables

if (DateTime.TryParse(dateString, out _)) {
	Console.WriteLine($"'{dateString}': valid"); 
}

5. Use it for null checks

_ = myVariable ?? throw new ArgumentNullException("IT'S A NULL");

6. If you assign a Task to it, it will suppress any exceptions thrown inside

 _ = Task.Run(() => { 
	var iterations = 0; 
	for (int ctr = 0; ctr < int.MaxValue; ctr++) iterations++; 
	Console.WriteLine("Completed looping operation..."); 
	throw new InvalidOperationException(); 
}); 

Where to go next?

As for me, I guess I will be returning to tuples. I hate tuples. They’re unreadable and often not helping. But I might change my mind.

Also, perhaps I will use discards for null checks.

End thoughts

This time I tried to keep everything concise. Instead of paragraphs with explanations I went to advanced text formatting. Headers and code snippets can be self-explaining and I will not waste your time.