"Discards"

static void Test() {
	// Just want to test if this is a valid value; we don't need the parsed value
	if (!Int32.TryParse(_userInput, out _)) {
		// ..
	}
	
	// Don't want the result of this method, just need to invoke it
	_ = _someInterface.SomeMethod();
	
	// Don't want to use these parameters in a lambda (C# 9+ only)
	_someInterface.DoThing((_, _, param3, _) => param3 == "hello"); 
}


Code snippet taken from "Two Decades of C#: A Reference - C# 7".