In my .NET8 MAUI application, I have a few functions for every platform but most of the code is the same. I saw somewhere that I could do something like:

#if iOS
    public async Task<string> Register(NSData rawToken)
    {
        var nativeToken = rawToken.ToPushTokenString();
#endif
#if ANDROID
    public async Task<string> Register(string nativeToken)
    { 
#endif
        // code
    }

I tried but Visual Studio disagrees and gets me an error. Is there any particular configuration I have to change? How does this pre-processor command work?