Letting employer know you're autistic

Hi everyone. I just wanted to know if anyone here has had a good experience of letting their employer know they're autistic, and then getting the support needed to do your job?

or

Have you let an employer know and it didn't really work in your favour?

I am just trying to weigh up the pros and cons as I think it might help me to let them know, but I am terrified of it having a negative outcome. I hate the thought of people within my workplace knowing I am autistic, but maybe if they did know, they could be more understanding when I struggle at times.

Thanks