How to uniquely idenitfy requests?

Remote API that I'm using, requires referenceId parameter that should uniquely identify each request. I don't want to increment numbers because I might send concurrent requests and moreover, I would need to save those numbers somewhere (for example if I decide to restart the application). referenceId should be all numbers, up to 48 characters. Could I generate a random 48-place number using RNGCryptoServiceProvider, would that be unique?