What version of Xamarin are you using?
If you are using the 'lastest' ios 8 Xamarin version please take a look here:
http://forums.xamarin.com/discussion/16489/new-type-registrar-in-xamarin-ios-7-2-1-errors-mt5210-and-mt5211So have you tried the mentioned workaround by using the "--registarar:legacy" linker option?!
The issue seems, that Xamarin now try to resolve ALL methods at once.
Meaning any external method defined within Bass.Net must physically exist (in the corresponding native BASS/add-on lib).
E.g. if you would include ALL referenced libs (like e.g. libbasswv.a, libbassopus.a, libbassmidi.a etc. etc.) then it should link/compile fine!
Can you confirm this?!
If not, please tell me which methods are exactly missing in case you really link against ALL native libs!
The problem is, that Bass.Net is ONE assembly, which defines ALL methods off ALL available native libs, bass AND any add-on.
If I read the new Xamarin docs correctly, they now check (by default), if all those defined external methods do actually exist.
This would mean, you MUST link against ALL native libs (bass and ALL add-ons).
If that is true, I can only say: how stupid is that! So you should contact Xamarin and file an issue with them.
It is not easy to change Bass.Net is that respect, as I would need to create for every native lib one related .net wrapper lib.
And this is in some cases not really possible right now!
So I think, we need to throw this issue back to Xamarin to find a solution.
I hope they have a switch/workaround for that.
Else, I am afraid, that you must really link against ALL native libs!
If all that also fails, I guess should 'ship' a sample application as a non-working example to the Xamarin support!