Is it OK to declare an async method as returning void to silence the CS4014 warning?

It's extremely rare to have a true fire-and-forget operation; that is, an operation where:

• No one cares when it completes.
• No one cares if it completes.
• No one cares if it throws an exception.

Particularly with the last of these; most so-called "fire-and-forget" operations are not actually fire-and-forget because some action needs to be taken if it doesn't succeed.

That said, there are a few situations where a true fire-and-forget is applicable.

I prefer to use async Task and avoid the compiler warning by assigning the task to an otherwise unused variable:

var _ = FireAndForget();

async Task methods are more reusable and testable than async void methods.

However, I wouldn't throw a fit if a developer on my team just used async void instead.

Is it OK to have a 'async void' method if the method is not designed to be awaitable in the first place and if no exception will be thrown?

Although it may be "OK" to do so, I would still encourage you to make the method async Task. Even though you are a 100 percent sure this method won't throw, and isn't ment to be awaited, you never know how it might end up getting used. You're now fully aware of what the consequences of using async void are, but if there's a slight chance that someone might need to use this in the future, then you're better of putting a nice comment on why this Task isn't being awaited instead of going with the easy path of making this void.

Don't let the compiler warnings worry you, I would say worry about the correctness and the effects this may have on your codebase.